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Sample records for photoinduced wolff rearrangement

  1. Evidence for Nonstatistical Dynamics in the Wolff Rearrangement of a Carbene

    PubMed Central

    2008-01-01

    Two 13C-labeled isomers of the formal Diels−Alder adduct of acetylmethyloxirene to tetramethyl 1,2,4,5-benzenetetracarboxylate have been synthesized. Flash vacuum thermolysis of these adducts leads to various isotopic isomers of acetylmethylketene, the ratios of which have been determined by NMR. The surprising finding that the principal product comes from methylpyruvoyl carbene rather than its more stable isomer diacetylcarbene is explained by MPWB1K density functional calculations, which show that the reactant probably undergoes a unimolecular rearrangement to a norcaradiene derivative prior to its fragmentation. Coupled-cluster calculations on the methylpyruvoyl carbene show that it is capable of undergoing three unimolecular isomerizations. The fastest is 1,2-acetyl migration to give acetylmethylketene directly. The next is rearrangement via acetylmethyloxirene to diacetylcarbene and thence by Wolff rearrangement to acetylmethylketene. The least-favorable reaction is degenerate rearrangement via 1,3-dimethyl-2-oxabicyclo[1.1.0]butan-4-one (the epoxide of dimethylcyclopropenone). The combined experimental and computational results indicate that Wolff rearrangement of the diacetylcarbene occurs with a 2.5:1 ratio of the methyl groups despite the fact that they are related by a twofold axis of symmetry in the carbene. Preliminary molecular dynamics simulations are consistent with this conclusion. Taken together, the results suggest that the Wolff rearrangement is subject to the same kind of nonstatistical dynamical effects detected for other kinds of thermally generated reactive intermediates. PMID:18700757

  2. Photoinduced Brook-Type Rearrangement of Acylcyclopolysilanes

    PubMed Central

    2013-01-01

    Previously unknown 1,1,4-tris(trimethylsilyl)-4-acyldodecamethylcyclohexasilanes (Me3Si)2Si6Me12(Me3Si)COR (16a, R = tert-butyl; 16b, R = 1-adamantyl) have been synthesized by the reaction of the potassium silanides (Me3Si)2Si6Me12(Me3Si)K with acid chlorides ClCOR, and their photochemical rearrangement reactions have been studied. The molecular structures of 16a,b as determined by single-crystal X-ray diffraction analysis exhibit an unusual twist-boat conformation of the cyclohexasilane ring. When 16a,b were photolyzed with λ >300 nm radiation, they underwent Brook type 1,3-Si → O migration reactions to generate the cyclohexasilanes 17a,b with exocyclic Si=C bonds along with smaller amounts of the ring-enlarged species 19a,b with endocyclic Si=C double bonds. While 17a,b were stable enough to allow characterization by NMR and UV absorption spectroscopy, the less stable products 19a,b could only be observed in the form of their methanol adducts. PMID:24465075

  3. Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

    PubMed Central

    Medvedev, Jury J; Galkina, Olesia S; Azarova, Ksenia V

    2016-01-01

    Summary Rh(II)-сatalyzed reactions of aroyldiazomethanes, diazoketoesters and diazodiketones with α,β-unsaturated δ-aminoesters, in contrast to reactions of diazomalonates and other diazoesters, give rise to the Wolff rearrangement and/or oxidative cleavage of the initially formed N–H-insertion products. These oxidation processes are mediated by Rh(II) catalysts possessing perfluorinated ligands. The formation of pyrrolidine structures, characteristic for catalytic reactions of diazoesters, was not observed in these processes at all. PMID:27829897

  4. Parallel Wolff Cluster Algorithms

    NASA Astrophysics Data System (ADS)

    Bae, S.; Ko, S. H.; Coddington, P. D.

    The Wolff single-cluster algorithm is the most efficient method known for Monte Carlo simulation of many spin models. Due to the irregular size, shape and position of the Wolff clusters, this method does not easily lend itself to efficient parallel implementation, so that simulations using this method have thus far been confined to workstations and vector machines. Here we present two parallel implementations of this algorithm, and show that one gives fairly good performance on a MIMD parallel computer.

  5. Scaling law of Wolff cluster surface energy

    NASA Astrophysics Data System (ADS)

    Hsiao, Pai-Yi; Monceau, Pascal

    2003-05-01

    We study the scaling properties of the clusters grown by the Wolff algorithm on seven different Sierpinski-type fractals of Hausdorff dimension 1Wolff cluster follows a power law with respect to the lattice size. Moreover, we investigate the probability density distribution of the surface energy of the Wolff cluster and are able to establish a different scaling relation. It enables us to introduce an exponent that is associated to the surface energy of the Wolff cluster. Finally, this exponent is linked to a dynamical exponent via an inequality.

  6. On the mechanism of photoinduced refractive index changes in phosphosilicate glass

    SciTech Connect

    Larionov, Yu V; Sokolov, V O; Plotnichenko, V G

    2010-05-26

    The photoinduced growth of the refractive index of phosphosilicate glass during Bragg grating inscription and the thermal decay of the grating have a number of unusual features. The observed index variations are interpreted in terms of a new model for photoinduced glass network rearrangement. The model assumes the formation of photoinduced voids (nanopores) in the glass network near point defects. The nanopores may migrate through the network via bond switching when the network is in a 'soft' state. The photoinduced variations in network density lead to index variations. (fibres)

  7. History of Wolff-Parkinson-White syndrome.

    PubMed

    Scheinman, Melvin M

    2005-02-01

    While Drs. Wolff, Parkinson, and White fully described the syndrome that bears their names in 1930, prior case reports had already described the essentials. Over the ensuing century this syndrome has captivated the interest of anatomists, clinical cardiologists, and cardiac surgeons. Stanley Kent described lateral muscular connections over the atrioventricular (AV) groove, which he felt were the normal AV connections. The normal AV connections were, however, clearly described by His and Tawara. True right-sided AV connections were initially described by Wood et al., while Ohnell first described left free wall pathways. David Scherf is thought to be the first to describe our current understanding of the pathogenesis of the Wolff-Parkinson-White (WPW) syndrome in terms of a reentrant circuit involving both the AV node--His axis as well as the accessory pathway. This hypothesis was not universally accepted and many theories were applied to explain the clinical findings. The basics of our understandings were established by the brilliant work of Pick, Langendorf, and Katz who by using careful deductive analysis of ECGs were able to define the basic pathophysiological processes. Subsequently, Wellens and Durrer applied invasive electrical stimulation to the heart in order to confirm the pathophysiological processes. Sealy and his colleagues at Duke University Medical Center were the first to successfully surgically divide an accessory pathway and ushered in the modern area for curative therapy for these patients. Morady and Scheinman were the first to successfully ablate an accessory pathway (posteroseptal) using high-energy direct-current shocks. Subsequently, Jackman, Kuck, Morady, and a number of groups proved the remarkable safety and efficiency of catheter ablation for pathways in all locations using radiofrequency energy. More recently, Gallob et al. first described the gene responsible for a familial form of WPW. The current ability to cure patients with WPW is

  8. Genetics Home Reference: Wolff-Parkinson-White syndrome

    MedlinePlus

    ... cause a disruption of the heart's normal rhythm (arrhythmia). The heartbeat is controlled by electrical signals that ... of breath, and fainting (syncope). In rare cases, arrhythmias associated with Wolff-Parkinson-White syndrome can lead ...

  9. [Wolff-Parkinson-White syndrome and cardiopathies].

    PubMed

    Soria, R; Fernandez, F; Heller, J; Brétille, J; Cherif, F; Barrillon, A; Gerbaux, A; Gay, J

    1984-12-01

    Forty-nine cases of Wolff-Parkinson-White syndrome (WPW) were diagnosed out of 10 750 patients with cardiac disease (0.45 p. 100), 24 cases out of 3 761 congenital malformations and 25 cases in the 6 989 patients with acquired heart disease. Right ventricular pre-excitation was recorded in 31 cases; 13 in the lateral zone, 12 in the posterior paraseptal zone and 6 in the anterior paraseptal zone. Left ventricular pre-excitation was recorded in 18 cases: 8 in the lateral zone, 5 in the anterior paraseptal and 5 in the posterior paraseptal zones. WPW and congenital heart disease: Out of 20 cases of Ebstein's anomaly, 5 cases of WPW were observed: 4 right posterior and 1 right lateral pre-excitations. Out of 218 cases of hypertrophic obstructive cardiomyopathy, 7 cases of WPW were observed, 4 of which were congenital. Three cases of WPW were recorded in 699 patients with ventricular septal defects. Out of 1 348 cases of atrial septal defect, 5 cases of pre-excitation were recorded, including 3 right posterior pre-excitations associated with an ostium primum defect. Pre-excitation was also observed in isolated cases of corrected transposition of the great arteries, supravalvular aortic stenosis, aortic incompetence and patent ductus arteriosus. Pre-excitation and acquired heart disease: Five cases of pre-excitation were recorded out of 305 cases of dilated cardiomyopathy (1.62 p. 100). Eleven cases of pre-excitation were recorded in a total of 3 471 cases of valvular heart disease (0.31 p. 100): 9 in rheumatic valve disease and 2 in mitral valve prolapse. Nine cases of pre-excitation were observed in 2 850 cases of coronary artery disease. Intermittent Wolff-Parkinson-White syndrome: Ventricular pre-excitation masks the ECG changes of complete right bundle branch block in Ebstein's anomaly, complete left bundle branch block in aortic incompetence and dilated cardiomyopathy, and the in-complete right bundle branch block often seen in mitral valve prolapse. The

  10. Charlotte Wolff and lesbian history: reconfiguring liminality in exile.

    PubMed

    Brennan, Toni; Hegarty, Peter

    2010-01-01

    This article considers the "liminality" of the psychologist Charlotte Wolff, MD (1897-1986). Always living openly as a lesbian since her school days in Danzig, Wolff trained as a doctor-also pursuing a parallel interest in poetry and in philosophy. As a Jewish person, she was forced to leave the Berlin Health Service and flee Germany when the Nazi regime came to power. Having moved to Great Britain in 1936 after three years in France, Wolff reconfigured "exile" beyond the literal experience of emigration and immigration, as a form of "marginality" or "liminality" always involved in artistic and scientific endeavors. In her life and work she negotiated several liminal areas-from her gender presentation to her standing in the academic and scientific community (she was a Fellow of the British Psychological Society, to which she bequeathed her papers and the copyright to her work, but at the same time she was not an eminent psychologist), to her membership of sexual minority organizations (she conducted pioneering research on lesbianism and bisexuality, but some resented her connection with the psy-professions). In the spirit of Wolff's "liminality" as a strategy and creative zone, and along the lines indicated by Morawski (1994) as regards the transformative possibilities of feminist psychology as a liminal science, we argue for a reappraisal of Wolff's life and work that, in negotiating the borderlands between lesbian history and history of psychology, could enrich both disciplines.

  11. Photoinduced Multicomponent Reactions.

    PubMed

    Garbarino, Silvia; Ravelli, Davide; Protti, Stefano; Basso, Andrea

    2016-12-12

    The combination of multicomponent approaches with light-driven processes opens up new scenarios in the area of synthetic organic chemistry, where the need for sustainable, atom- and energy-efficient reactions is increasingly urgent. Photoinduced multicomponent reactions are still in their infancy, but significant developments in this area are expected in the near future.

  12. Caring for the Student with Wolff-Parkinson-White Syndrome

    ERIC Educational Resources Information Center

    Prenni, Patricia G.

    2009-01-01

    Wolff-Parkinson-White syndrome is a cardiac condition in which an extra electrical pathway within the heart causes an abnormal increase in heart rate. It affects one to three people of every 1,000 people worldwide, occurring more often in males. Diagnosis usually occurs during young adulthood, so it is important for school nurses to be familiar…

  13. Photoinduced diffusion molecular transport

    NASA Astrophysics Data System (ADS)

    Rozenbaum, Viktor M.; Dekhtyar, Marina L.; Lin, Sheng Hsien; Trakhtenberg, Leonid I.

    2016-08-01

    We consider a Brownian photomotor, namely, the directed motion of a nanoparticle in an asymmetric periodic potential under the action of periodic rectangular resonant laser pulses which cause charge redistribution in the particle. Based on the kinetics for the photoinduced electron redistribution between two or three energy levels of the particle, the time dependence of its potential energy is derived and the average directed velocity is calculated in the high-temperature approximation (when the spatial amplitude of potential energy fluctuations is small relative to the thermal energy). The thus developed theory of photoinduced molecular transport appears applicable not only to conventional dichotomous Brownian motors (with only two possible potential profiles) but also to a much wider variety of molecular nanomachines. The distinction between the realistic time dependence of the potential energy and that for a dichotomous process (a step function) is represented in terms of relaxation times (they can differ on the time intervals of the dichotomous process). As shown, a Brownian photomotor has the maximum average directed velocity at (i) large laser pulse intensities (resulting in short relaxation times on laser-on intervals) and (ii) excited state lifetimes long enough to permit efficient photoexcitation but still much shorter than laser-off intervals. A Brownian photomotor with optimized parameters is exemplified by a cylindrically shaped semiconductor nanocluster which moves directly along a polar substrate due to periodically photoinduced dipole moment (caused by the repetitive excited electron transitions to a non-resonant level of the nanocylinder surface impurity).

  14. Photo-induced structural changes in Ge-Sb-Se films

    NASA Astrophysics Data System (ADS)

    Lin, Li; Wang, Guoxiang; Shen, Xiang; Dai, Shixun; Xu, Tiefeng; Nie, Qiuhua

    2017-03-01

    Amorphous Ge-Sb-Se thin films have been prepared by the radio-frequency (RF) magnetron co-sputtering deposition technique, and their intrinsic photosensitivity and photo-induced structural changes have been investigated. The results show a crossover from photodarkening (PD) to photobleaching (PB) in the films when the film compositions change from Se-deficient to rich. Further Raman analysis on these as-prepared thin films irradiated with a laser of wavelength 655 nm in every five minutes provides direct evidence of photo-induced structure rearrangements.

  15. Critical Dynamics Behavior of the Wolff Algorithm in the Site-Bond-Correlated Ising Model

    NASA Astrophysics Data System (ADS)

    Campos, P. R. A.; Onody, R. N.

    Here we apply the Wolff single-cluster algorithm to the site-bond-correlated Ising model and study its critical dynamical behavior. We have verified that the autocorrelation time diminishes in the presence of dilution and correlation, showing that the Wolff algorithm performs even better in such situations. The critical dynamical exponents are also estimated.

  16. Asymptomatic Wolff-Parkinson-White Syndrome: Who Should Be Treated?

    PubMed

    Obeyesekere, Manoj N; Leong-Sit, Peter; Krahn, Andrew D; Gula, Lorne J; Yee, Raymond; Skanes, Allan C; Klein, George J

    2012-09-01

    This article discusses the merits of electrophysiology study (EPS) and/or ablation for asymptomatic preexcitation Wolff-Parkinson-White (WPW) ECG pattern. Sudden deaths in asymptomatic patients are too few to merit broad screening and aggressive intervention. It also discusses the risks of ablation and the low predictive accuracy of EPS. When WPW is an incidental finding, the decision to proceed with investigation and ablation can be made considering patients' situations and preferences. An invasive strategy is targeted at patients concerned about the low risk of life-threatening arrhythmia as a first presentation after a discussion of the risks and benefits.

  17. Degradations and Rearrangement Reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Jianbo

    This section deals with recent reports concerning degradation and rearrangement reactions of free sugars as well as some glycosides. The transformations are classified in chemical and enzymatic ways. In addition, the Maillard reaction will be discussed as an example of degradation and rearrangement transformation and its application in current research in the fields of chemistry and biology.

  18. Wolff-Parkinson-White syndrome: lessons learnt and lessons remaining.

    PubMed

    Benson, D Woodrow; Cohen, Mitchell I

    2017-01-01

    The Wolff-Parkinson-White pattern refers to the electrocardiographic appearance in sinus rhythm, wherein an accessory atrioventricular pathway abbreviates the P-R interval and causes a slurring of the QRS upslope - the "delta wave". It may be asymptomatic or it may be associated with orthodromic reciprocating tachycardia; however, rarely, even in children, it is associated with sudden death due to ventricular fibrillation resulting from a rapid response by the accessory pathway to atrial fibrillation, which itself seems to result from orthodromic reciprocating tachycardia. Historically, patients at risk for sudden death were characterised by the presence of symptoms and a shortest pre- excited R-R interval during induced atrial fibrillation <250 ms. Owing to the relatively high prevalence of asymptomatic Wolff-Parkinson-White pattern and availability of catheter ablation, there has been a need to identify risk among asymptomatic patients. Recent guidelines recommend invasive evaluation for such patients where pre-excitation clearly does not disappear during exercise testing. This strategy has a high negative predictive value only. The accuracy of this approach is under continued investigation, especially in light of other considerations: Patients having intermittent pre-excitation, once thought to be at minimal risk may not be, and the role of isoproterenol in risk assessment.

  19. Relevance of collagen piezoelectricity to "Wolff's Law": a critical review.

    PubMed

    Ahn, Andrew C; Grodzinsky, Alan J

    2009-09-01

    According to "Wolff's Law", bone is deposited and reinforced at areas of greatest stress. From a clinical perspective, this "law" is supported by the strong association between bone density and physical activity. From a mechanistic standpoint, however, the law presents a challenge to scientists seeking to understand how osteocytes and osteoblasts sense the mechanical load. In the 1960s, collagen piezoelectricity was invoked as a potential mechanism by which osteocytes could detect areas of greater stress but piezoelectricity diminished in importance as more compelling mechanisms, such as streaming potential, were identified. In addition, accumulating evidence for the role of fluid-related shear stress in osteocyte's mechanosensory function has made piezoelectricity seemingly more obsolete in bone physiology. This review critically evaluates the role of collagen piezoelectricity (if any) in Wolff's Law--specifically, the evidence regarding its involvement in strain-generated potentials, existing alternate mechanisms, the present understanding of bone mechanosensation, and whether piezoelectricity serves an influential role within the context of this newly proposed mechanism. In addition to reviewing the literature, this review generates several hypotheses and proposes future research to fully address the relevance of piezoelectricity in bone physiology.

  20. [Unusual supraventricular tachycardias in Wolff-Parkinson-White syndrome].

    PubMed

    Belhassen, B; Laniado, S

    1983-01-01

    Two unusual types of narrow-QRS tachycardias were initiated during electrophysiological investigation of a patient with the Wolff-Parkinson-White syndrome. In the first type, the QRS complexes were preceded by atrial activation, the chronological sequence of depolarisation of which was similar to the sinus rhythm, suggesting the mechanism of sino-atrial reentry. The narrow QRS complex during tachycardia was related to the fact that the refractory period of the accessory pathway was longer than the tachycardia cycle. The second type of tachycardia was associated with I/I retrograde atrial activation within the QRS complex, suggesting the mechanism of intranodal reentry. The main point of interest of this case is that the accessory pathway, which only conducted in the anterograde direction, did not participate in the mechanism of either of these tachycardias.

  1. Acceleration of ventricular rate by fibrillation associated with the Wolff-Parkinson-White syndrome.

    PubMed

    Sheinman, B D; Evans, T

    1982-10-09

    Amiodarone has proved to be a valuable drug in atrial fibrillation associated with the Wolff-Parkinson-White syndrome. When it was administered to a patient with this syndrome in atrial fibrillation, who had previously suffered an inferior myocardial infarction, the ventricular rate accelerated from 170 to 230 beats/minute.This unusual case emphasises the need for full electrophysiological assessment of patients with the Wolff-Parkinson-White syndrome for whom amiodarone treatment is being considered.

  2. The cubyl cation rearrangements.

    PubMed

    Jalife, Said; Mondal, Sukanta; Cabellos, Jose Luis; Martinez-Guajardo, Gerardo; Fernandez-Herrera, Maria A; Merino, Gabriel

    2016-02-25

    Born-Oppenheimer molecular dynamics simulations and high-level ab initio computations predict that the cage-opening rearrangement of the cubyl cation to the 7H(+)-pentalenyl cation is feasible in the gas phase. The rate-determining step is the formation of the cuneyl cation with an activation barrier of 25.3 kcal mol(-1) at the CCSD(T)/def2-TZVP//MP2/def2-TZVP level. Thus, the cubyl cation is kinetically stable enough to be formed and trapped at moderate temperatures, but it may be rearranged at higher temperatures.

  3. Wolff-Parkinson-White Syndrome--current views.

    PubMed

    Chung, E K

    1977-02-01

    The Wolff-Parkinson-White (WPW) syndrome is an important clinical entity because of frequent recurrences of very rapid tachyarrhythmias. The electrocardiographic finding of the WPW syndrome often mimicks pseudo diaphragmatic (inferior) myocardial infarction which should not be misinterpreted. The most important diagnostic criterion is recognition of a delta wave; the short P-R interval or broad QRS complex may not be present in every case. The mechanism for the tachycardia is considered to be a reentry phenomenon via anomalous and normal atrioventricllar (A-V) pathways. The drug of choice for the treatment of regular supraventricular (reciprocating) tachycardia with narrow QRS complexes, which is the most common arrhythmia in the WPW syndrome, is propranolol. Digitalis is almost equally effective in this case. For tachyarrhythmias, particularly atrial fibrillation or flutter with anomalous conduction, intravenously-administered lidocaine is considered to be the drug of choice. Procainamide or quinidine is also frequently used under this circumstance with excellent therapeutic result. Many patients with the WPW syndrome require long-term maintenance drug therapy (propranolol, digitalis or quinidine in most cases). In urgent clinical situations, direct current (DC) shock should be applied immediately. In selected patients with refractory tachyarrhythmias, the use of an artificial pacemaker or surgical approach may be considered.

  4. [Outcome of 195 patients with Wolff-Parkinson-White syndrome].

    PubMed

    Brembilla-Perrot, B; Aliot, E; Louis, P; Terrier de la Chaise, A; Khalife, K; Marçon, F; Cherrier, F; Gilgenkrantz, J M; Pernot, C

    1987-03-01

    Between 1974 and 1984, 207 patients with Wolff-Parkinson-White syndrome (WPW) were admitted to our hospital department; 195 of them were followed up for periods ranging from 1 to 12 years (6 years in children, 3 years and 9 months in adults on average); 160 had undergone electrophysiological exploration. Fifty-seven patients were less than 16 years old: 7 died, including 6 with associated congenital heart disease; an asymptomatic 12-year old girl died suddenly while taking part in a sporting event. The signs of WPW disappeared in 5 out of 10 children under 1 year of age. One hundred and thirty-eight patients were older than 15: 15 of them died, but only 3 deaths were related to WPW: one was consecutive to surgery for WPW and one to fulguration; the third patient died of WPW tachyarrhythmia; the refractory period of his Kent's bundle was short, but his compliance with treatment was irregular. We found no correlation between changes in functional symptoms and Kent's bundle refractory period values; paradoxically, the frequency of attacks and resistance to treatment was higher in cases with long refractory period. On the whole, this series confirms that WPW usually is a benign disease. However, the risk of sudden death, of which it offers an example, indicates that all patients with WPW should be evaluated with at least an exercise test and, depending on its results or on the socio-professional context, an electrophysiological exploration.

  5. Parallelization of the Wolff single-cluster algorithm

    NASA Astrophysics Data System (ADS)

    Kaupužs, J.; Rimšāns, J.; Melnik, R. V. N.

    2010-02-01

    A parallel [open multiprocessing (OpenMP)] implementation of the Wolff single-cluster algorithm has been developed and tested for the three-dimensional (3D) Ising model. The developed procedure is generalizable to other lattice spin models and its effectiveness depends on the specific application at hand. The applicability of the developed methodology is discussed in the context of the applications, where a sophisticated shuffling scheme is used to generate pseudorandom numbers of high quality, and an iterative method is applied to find the critical temperature of the 3D Ising model with a great accuracy. For the lattice with linear size L=1024 , we have reached the speedup about 1.79 times on two processors and about 2.67 times on four processors, as compared to the serial code. According to our estimation, the speedup about three times on four processors is reachable for the O(n) models with n≥2 . Furthermore, the application of the developed OpenMP code allows us to simulate larger lattices due to greater operative (shared) memory available.

  6. Parallelization of the Wolff single-cluster algorithm.

    PubMed

    Kaupuzs, J; Rimsāns, J; Melnik, R V N

    2010-02-01

    A parallel [open multiprocessing (OpenMP)] implementation of the Wolff single-cluster algorithm has been developed and tested for the three-dimensional (3D) Ising model. The developed procedure is generalizable to other lattice spin models and its effectiveness depends on the specific application at hand. The applicability of the developed methodology is discussed in the context of the applications, where a sophisticated shuffling scheme is used to generate pseudorandom numbers of high quality, and an iterative method is applied to find the critical temperature of the 3D Ising model with a great accuracy. For the lattice with linear size L=1024, we have reached the speedup about 1.79 times on two processors and about 2.67 times on four processors, as compared to the serial code. According to our estimation, the speedup about three times on four processors is reachable for the O(n) models with n> or =2. Furthermore, the application of the developed OpenMP code allows us to simulate larger lattices due to greater operative (shared) memory available.

  7. Photo-induced Defects in Semiconductors

    NASA Astrophysics Data System (ADS)

    Redfield, David; Bube, Richard H.

    2006-03-01

    1. Introduction: metastable defects; 2. III-V compounds: DX2 and EL2 centers; 3. Other crystalline materials; 4. Hydrogenated amorphous silicon: properties of defects; 5. Hydrogenated amorphous silicon: photo-induced defect kinetics and processes; 6. Other amorphous semiconductors; 7. Photo-induced defect effects in devices; References; Index.

  8. Phosphonate–Phosphinate Rearrangement

    PubMed Central

    2014-01-01

    LiTMP metalated dimethyl N-Boc-phosphoramidates derived from 1-phenylethylamine and 1,2,3,4-tetrahydronaphthalen-1-ylamine highly selectively at the CH3O group to generate short-lived oxymethyllithiums. These isomerized to diastereomeric hydroxymethylphosphonamidates (phosphate–phosphonate rearrangement). However, s-BuLi converted the dimethyl N-Boc-phosphoramidate derived from 1-phenylethylamine to the N-Boc α-aminophosphonate preferentially. Only s-BuLi deprotonated dimethyl hydroxymethylphosphonamidates at the benzylic position and dimethyl N-Boc α-aminophosphonates at the CH3O group to induce phosphonate–phosphinate rearrangements. In the former case, the migration of the phosphorus substituent from the nitrogen to the carbon atom followed a retentive course with some racemization because of the involvement of a benzyllithium as an intermediate. PMID:25525945

  9. The history of the wolff-Parkinson-white syndrome.

    PubMed

    Scheinman, Melvin M

    2012-07-01

    While Drs Wolff, Parkinson, and White fully described the syndrome in 1930, prior case reports had described the essentials. Over the ensuing century this syndrome has captivated the interest of anatomists, clinical cardiologists, and cardiac surgeons. Stanley Kent described lateral muscular connections over the atrioventricular (AV) groove which he felt were the normal AV connections. The normal AV connections were, however, clearly described by His and Tawara. True right-sided AV connections were initially described by Wood et al., while Öhnell first described left free wall pathways. David Scherf is thought to be the first to describe our current understanding of the pathogenesis of the WPW syndrome in terms of a re-entrant circuit involving both the AV node-His axis as well as the accessory pathway. This hypothesis was not universally accepted, and many theories were applied to explain the clinical findings. The basics of our understanding were established by the brilliant work of Pick, Langendorf, and Katz who by using careful deductive analysis of ECGs were able to define the basic pathophysiological processes. Subsequently, Wellens and Durrer applied invasive electrical stimulation to the heart in order to confirm the pathophysiological processes. Sealy and his colleagues at Duke University Medical Center were the first to successfully surgically divide an accessory pathway and ushered in the modern era of therapy for these patients. Morady and Scheinman were the first to successfully ablate an accessory pathway (posteroseptal) using high-energy direct-current shocks. Subsequently Jackman, Kuck, Morady, and a number of groups proved the remarkable safety and efficiency of catheter ablation for pathways in all locations using radiofrequency energy. More recently, Gollob et al. first described the gene responsible for a familial form of WPW. The current ability to cure patients with WPW is due to the splendid contributions of individuals from diverse

  10. [Electrophysiological characteristics of asymptomatic Wolff-Parkinson-White syndromes].

    PubMed

    Brembilla-Perrot, B; Ghawi, R; Dechaux, J P

    1991-11-01

    The management of the Wolff-Parkinson-White syndrome (WPW) is controversial especially when the patient is asymptomatic. The aim of this study was to evaluate the electrophysiological characteristics of such patients. Thirty two asymptomatic subjects with overt WPW on the surface ECG aged 14 to 68 years (average 36 +/- 15 years) underwent endocavitary or oesophageal electrophysiological study with the following protocol: programmed atrial stimulation using 1 or 2 extrastimuli over 3 cycles to evaluate the induction of paroxysmal junctional tachycardia and atrial fibrillation; atrial pacing at increasing frequencies to assess the shortest cycle conducted by the bundle of Kent. This protocol was repeated during intravenous infusion of 20 to 30 mg of Isoproterenol. Four electrophysiological characteristics were identified: the incidence of induction of junctional tachycardia was very low (2 cases, 6%); the incidence of induction of atrial fibrillation or tachycardia was similar to that of symptomatic WPW (9 cases 30%); the incidence of rapid conduction via the bundle of Kent (cycle conducted by the Kent less than 250 ms under basal conditions less than 200 ms with Isoproterenol) was 19% (6 cases); the incidence of potentially serious forms of WPW with rapid conduction in the bundle of Kent and atrial vulnerability (induction of atrial fibrillation at a frequency less than the Wenckebach point by programmed atrial stimulation) was similar to that in symptomatic WPW, 3 cases (10%). In conclusion, the asymptomatic character of the WPW is very probably due to the absence of junctional tachycardias. Nevertheless, these patients are at risk of atrial fibrillation with an incidence of potentially serious forms of 10%.(ABSTRACT TRUNCATED AT 250 WORDS)

  11. [Oral propranolol in Wolff-Parkinson-White syndrome. Electrophysiological data].

    PubMed

    Dolla, E; Levy, S; Cointe, R; Moyal, C; Bru, P; Rossi, P; Gérard, R

    1991-07-01

    The effects of oral propranolol were studied in 24 patients with the WPW syndrome. The average daily dose of propranolol was 130 +/- 24 mg administered in 3 doses over a period of 48 to 72 hours. Endocavitary electrophysiological study was performed 2 to 4 hours after the last dose. The effective anterograde refractory periods (EARP) of the accessory and normal pathways were measured before and after propranolol (and, in both studies, before and after isoproterenol). The EARP of the accessory pathway was not affected by the propranolol. However, in the 9 patients in whom its value was less than 270 ms, it increased significantly (p = 0.01). The EARP of the accessory pathway measured after administration of isoproterenol increased significantly in all patients with oral propranolol (p = 0.001). Sustained reciprocating tachycardia could be induced in 19 patients and non-sustained reciprocating tachycardia in 5 other patients during base line electrophysiological study. Oral propranolol prevented the induction of the tachycardias in 18 patients (75%), even after isoproterenol. The shortest R-R interval between two pre-excited complexes in atrial fibrillation increased after propranolol (283 +/- 45 to 343 +/- 95 ms). These results show that oral propranolol increases the EARP of the accessory pathway and the shortest R-R interval between two pre-excited complexes in atrial fibrillation in patients with short anterograde refractory periods of their accessory pathways, and is effective in preventing reciprocating tachycardia. Oral propranolol may be useful and can be used safely in patients with the Wolff-Parkinson-White syndrome.

  12. [Ventricular fibrillation in Wolff-Parkinson-White syndrome. Predictive factors].

    PubMed

    Attoyan, C; Haissaguerre, M; Dartigues, J F; Le Métayer, P; Warin, J F; Clémenty, J

    1994-07-01

    The incidence of sudden death in the Wolff-Parkinson-White (WPW) syndrome is not well documented and probably underestimated. This retrospective study concerned 28 consecutive patients presenting with ventricular fibrillation either spontaneously (20) or during electrophysiological investigation (8) but whose characteristics allowed them to be assimilated into a single group. Their clinical and electrophysiological characteristics were compared with those of 60 consecutive patients with the WPW syndrome who had documented atrial fibrillation (and even reciprocating tachycardia) but never ventricular fibrillation. There were no significant differences between the two groups with respect to the following clinical parameters: sex, duration of symptoms, the type of tachycardia previously recorded, history of syncope and presence of underlying cardiac disease. With respect to the electrophysiological data, there were no differences in the point of anterograde block, the effective anterograde refractory period of the accessory pathway, the effective and functional refractory periods of the right atrium and atrial vulnerability. On the other hand, a significant difference was observed in the age of patients with ventricular fibrillation (29 +/- 13 years vs 36 +/- 12 years; p < 0.02), the prevalence of multiple accessory pathways (25% vs 7%; p < 0.04) with a dominant localisation in the postero-septal region (75% vs 47%, p < 0.026), preexcitation during exercise stress testing and under antiarrhythmic therapy (95% vs 68%, p < 0.037). The most discriminating parameter was the shorter RR interval during atrial fibrillation (172 +/- 23 ms vs 230 +/- 50 ms, p < 0.008). Multivariate analysis only showed one independent predictive factor: the minimum preexcited RR interval.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Wolff algorithm and anisotropic continuous-spin models: An application to the spin-van der Waals model

    NASA Astrophysics Data System (ADS)

    D'onorio de Meo, Marco; Oh, Suhk Kun

    1992-07-01

    The problem of applying Wolff's cluster algorithm to anisotropic classical spin models is resolved by modifying a part of the Wolff algorithm. To test the effectiveness of our modified algorithm, the spin-van der Waals model is investigated in detail. Our estimate of the dynamical exponent of the model is z=0.19+/-0.04.

  14. [Surgical atrioventricular disconnection in Wolff-Parkinson-White syndrome].

    PubMed

    Pavie, A; Mesnildrey, P; Gandjbakhch, I; Cabrol, C; Fontaine, G; Franck, R; Grosgogeat, Y; Slama, R

    1984-06-01

    Surgical atrioventricular disconnection is a possible means of treating patients with severe paroxysmal arrhythmias resistant to medical treatment due to the Wolff-Parkinson-White syndrome. Between 1971 and April 1982 we operated 50 patients (38 men and 12 women) with the WPW syndrome. Thirty seven patients were operated for arrhythmias (paroxysmal tachycardia) resistant to medical therapy or with a high risk of sudden death. Thirteen patients had associated cardiac disease with less severe arrhythmias (aortic valve disease: 6 cases; mitral and aortic valve disease: 3 cases; mitral valve disease: 3 cases, and atrial septal defect: 1 case). The causes of paroxysmal tachycardia were atrial fibrillation (13 cases), atrial flutter (2 cases), orthodromic reciprocating tachycardia (30 cases), with associated atrial fibrillation in 9 cases, and with associated atrial flutter in 4 cases. Antidromic reciprocating tachycardia was present in 2 cases. In 3 cases, the preexcitation was a chance finding. Electrophysiological studies performed before and after antiarrhythmic drug administration showed type A WPW (LV preexcitation) in 23 cases, and type B WPW (RV preexcitation) in 20 cases. The ECG was normal in the horizontal plane in 7 cases. The atrioventricular accessory pathway was permeable in both directions in 39 cases; in 9 cases the pathway was permeable only in the retrograde direction and in 2 cases it was permeable only in the anterograde direction. In 7 patients an atrio-hisian short circuit was demonstrated. The site of the accessory conduction pathway was located by epicardial mapping, the first surgical stage, in the left lateral region of the atrioventricular junction (28 cases), in the right lateral region (6 cases), in the posterior septal region (15 cases) (right sided in 4 cases, left sided in 11 cases), and in the anterior septal region (1 case). The accessory pathway (so-called Bundle of Kent) was interrupted by atrioventricular disconnection. Six patients

  15. Photoinduced Intramolecular Cyclopentanation vs Photoprotolytic Oxametathesis in Polycyclic Alkenes Outfitted with Conformationally Constrained Aroylmethyl Chromophores‡

    PubMed Central

    Valiulin, Roman A.; Arisco, Teresa M.; Kutateladze, Andrei G.

    2012-01-01

    Intramolecular photoinduced cyclizations are investigated in photoprecursors assembled in a modular fashion via a Diels-Alder reaction of acetylenic dienophiles with subsequent Michael additions of aromatic ketones to install a chromophore capable of initiating Paternò-Büchi cycloadditions or radical cyclization cascades. The protolytic oxametathesis in these systems allows for rapid access to novel polycyclic scaffolds decorated by formyl groups and carboxylates suitable for subsequent modifications. In conformationally constrained photoprecursors a radical rearrangement takes place resulting in intramolecular 1,3-diradical cyclopentanation of the double bond. PMID:23106813

  16. Multifractal analysis of photoinduced cooperative phenomena

    NASA Astrophysics Data System (ADS)

    Ishida, Kunio; Nasu, Keiichiro

    2008-01-01

    We study the multifractal properties of the geometrical patterns which appear in the initial processes of photoinduced structural change. Employing a model of localized electrons coupled with a single-phonon mode, we calculate the Lipschitz-Hölder exponent α and singularity spectrum f(α) on the distribution of excited electronic states and molecular distortion by using the box-counting method, and discuss the temporal behavior of photoinduced domains.

  17. Wolff-Michael Roth's passibility: at the limits of the constructivist metaphor: a book review

    NASA Astrophysics Data System (ADS)

    Brendel, Michelle

    2014-12-01

    Wolff-Michael Roth deconstructs the preeminent role conceded to constructivism in Science Education and demonstrates how we learn and know through pain, suffering, love or passion. This review explores his book "Passibility: At the Limits of the Constructivist Metaphor" through the eyes of an outsider to the world of science education.

  18. A Hydrazine-Free Wolff-Kishner Reaction Suitable for an Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Cranwell, Philippa B.; Russell, Andrew T.

    2016-01-01

    A Wolff-Kishner reaction that does not require hydrazine has been developed. The reaction sequence has two steps: formation of a carbomethoxyhydrazone from methyl hydrazinocarboxylate and acetophenone, then decomposition of this intermediate by treatment with potassium hydroxide in triethylene glycol. Purification is by filtration through a plug…

  19. [Significance of tachycardia induced by atrial stimulation in Wolff-Parkinson-White syndrome].

    PubMed

    Brembilla-Perrot, B

    1992-04-01

    Increased atrial vulnerability is one of the criteria of malignant Wolff-Parkinson-White syndrome. The aim of this study was to try to define the methods of induction of atrial tachycardias (tachycardia, flutter, fibrillation) by endocavitary and oesophageal stimulation characterising an increased vulnerability. The incidence of induced sustained tachycardia by fixed atrial stimulation at incremental rates until the Wenckebach point is attained and programmed atrial stimulation using 1 and 2 extrastimuli under basal conditions and then with isoproterenol was compared in subjects without cardiac disease, Wolff-Parkinson-White or spontaneous tachycardia (Group I) and patients with Wolff-Parkinson-White and spontaneous tachycardias (Group II). Atrial stimulation only induced tachycardia in 2.5% of normal subjects under basal conditions or with isoproterenol, by the endocavitary or oesophageal approaches. Programmed stimulation induced tachycardia in 15% of normal subjects under basal conditions or with isoproterenol by the endocavitary approach alone. In Group II, tachycardia was reproduced under basal conditions or with isoproterenol by atrial stimulation or programmed stimulation in all patients. In conclusion, the induction of a tachyarrhythmia by incremental atrial stimulation up to the Wenckebach point is always pathological even with isoproterenol. Programmed atrial stimulation is less specific except by the oesophageal approach. The use of bursts of very rapid stimuli in the Wolff-Parkinson-White syndrome is of no value as tachycardia can be induced by classical methods in all subjects at risk.

  20. [Wolff-Parkinson-White syndrome in a case of acute rejection of cardiac transplantation].

    PubMed

    Ollitrault, J; Daubert, J C; Ramée, M P; Ritter, P; Mabo, P; Leguerrier, A; Rioux, C; Logeais, Y

    1990-09-01

    A Wolff-Parkinson-White syndrome was observed during acute rejection in a patient who had undergone orthotopic cardiac transplantation. The sometimes intermittent nature of this syndrome could explain its postoperative appearance in this patient; the relationship with the episode of rejection is discussed.

  1. Alternating Wolff-Parkinson-White syndrome associated with attack of angina

    SciTech Connect

    Mangiafico, R.A.; Petralito, A.; Grimaldi, D.R. )

    1990-07-01

    In a patient with Wolff-Parkinson-White syndrome and an inferior-posterior bypass tract, transient restoration of normal conduction occurred during an attack of angina. The ECG pattern of inferior posterior ischemia was present when the conduction was normal. Thallium scintigraphy showed a reversible posterolateral perfusion defect. The possible mechanisms for production of intermittent preexcitation are discussed.

  2. Subjectivity and Cultural Adjustment in Mathematics Education: A Response to Wolff-Michael Roth

    ERIC Educational Resources Information Center

    Brown, Tony

    2012-01-01

    In this volume, Wolff-Michael Roth provides a critical but partial reading of Tony Brown's book "Mathematics Education and Subjectivity". The reading contrasts Brown's approach with Roth's own conception of subjectivity as derived from the work of Vygotsky, in which Roth aims to "reunite" psychology and sociology. Brown's book, however, focuses on…

  3. How to maintain the oral health of a child with Wolff-Parkinson-White syndrome: a case report

    PubMed Central

    2014-01-01

    Introduction Wolff-Parkinson-White syndrome is one of the most important disorders of the heart conduction system. It is caused by the presence of an abnormal accessory electrical conduction pathway between the atria and the ventricles. Case presentation In the present report, we describe the correct oral health management of a 12-year-old Caucasian girl with Wolff-Parkinson-White syndrome. Conclusions We successfully undertook the dental care of a girl with Wolff-Parkinson-White syndrome, which we describe here. PMID:25269932

  4. Genomic Rearrangements in Prostate Cancer

    PubMed Central

    Barbieri, Christopher E.; Rubin, Mark A.

    2014-01-01

    Purpose of review Genomic instability is a fundamental feature of human cancer, leading to the activation of oncogenes and inactivation of tumor suppressors. In prostate cancer, structural genomic rearrangements, resulting in gene fusions, amplifications and deletions, are a critical mechanism effecting these alterations. Here we review recent literature regarding the importance of genomic rearrangements in the pathogenesis of prostate cancer and the potential impact on patient care. Recent findings Next generation sequencing has revealed a striking abundance, complexity, and heterogeneity of genomic rearrangements in prostate cancer. These recent studies have nominated a number of processes in predisposing prostate cancer to genomic rearrangements, including androgen-induced transcription. Summary Structural rearrangements are the critical mechanism resulting in the characteristic genomic changes associated with prostate cancer pathogenesis and progression. Future studies will determine if the impact of these events on tumor phenotypes can be translated to clinical utility for patient prognosis and choices of management strategies. PMID:25393273

  5. Capturing ultrafast photoinduced local structural distortion of BiFeO3

    SciTech Connect

    Wen, Haidan; Sassi, Michel; Luo, Zhenlin; Adamo, Carolina; Schlom, Darrell G.; Rosso, Kevin M.; Zhang, Xiaoyi

    2015-10-14

    The interaction of light with materials is an intensively studied research forefront, in which the coupling of radiation energy to selective degrees of freedom offers contact-free tuning of functionalities on ultrafast time scales. Capturing the fundamental processes and understanding the mechanism of photoinduced structural rearrangement are essential to applications such as photo-active actuators and efficient photovoltaic devices. Using ultrafast x-ray absorption spectroscopy aided by density functional theory calculations, we reveal the local structural arrangement around the transition metal atom in a unit cell of the photoferroelectric archetype BiFeO3 film. The out-of-plane elongation of the unit cell is accompanied by the in-plane shrinkage with minimal change of interaxial lattice angles upon photoexcitation. This anisotropic elastic deformation of the unit cell is driven by localized electric field as a result of photoinduced charge separation, in contrast to a global lattice constant increase and lattice angle variations as a result of heating. The finding of a photoinduced elastic unit cell deformation elucidates a microscopic picture of photocarrier-mediated non-equilibrium processes in polar materials.

  6. Capturing ultrafast photoinduced local structural distortions of BiFeO3

    SciTech Connect

    Wen, Haidan; Sassi, Michel JPC; Luo, Zhenlin; Adamo, Carolina; Schlom, Darrell; Rosso, Kevin M.; Zhang, Xiaoyi

    2015-10-14

    The interaction of light with materials is an intensively studied research forefront, in which the coupling of radiation energy to selective degrees of freedom offers contact-free tuning of functionalities on ultrafast time scales. Capturing the fundamental processes and understanding the mechanism of photoinduced structural rearrangement are essential to applications such as photo-active actuators and efficient photovoltaic devices. Using ultrafast x-ray absorption spectroscopy aided by density functional theory calculations, we reveal the local structural arrangement around the transition metal atom in a unit cell of the photoferroelectric archetype BiFeO3 film. The out-of-plane elongation of the unit cell is accompanied by the in-plane shrinkage with minimal change of interaxial lattice angles upon photoexcitation. This uniaxial elastic deformation of the unit cell is driven by localized electric field as a result of photoinduced charge separation, in contrast to a global lattice constant increase and lattice angle variations as a result of heating. The finding of a photoinduced elastic unit cell deformation elucidates a microscopic picture of photocarrier-mediated nonequilibrium processes in polar materials.

  7. Capturing ultrafast photoinduced local structural distortions of BiFeO3

    DOE PAGES

    Wen, Haidan; Sassi, Michel JPC; Luo, Zhenlin; ...

    2015-10-14

    The interaction of light with materials is an intensively studied research forefront, in which the coupling of radiation energy to selective degrees of freedom offers contact-free tuning of functionalities on ultrafast time scales. Capturing the fundamental processes and understanding the mechanism of photoinduced structural rearrangement are essential to applications such as photo-active actuators and efficient photovoltaic devices. Using ultrafast x-ray absorption spectroscopy aided by density functional theory calculations, we reveal the local structural arrangement around the transition metal atom in a unit cell of the photoferroelectric archetype BiFeO3 film. The out-of-plane elongation of the unit cell is accompanied by themore » in-plane shrinkage with minimal change of interaxial lattice angles upon photoexcitation. This uniaxial elastic deformation of the unit cell is driven by localized electric field as a result of photoinduced charge separation, in contrast to a global lattice constant increase and lattice angle variations as a result of heating. The finding of a photoinduced elastic unit cell deformation elucidates a microscopic picture of photocarrier-mediated nonequilibrium processes in polar materials.« less

  8. Capturing ultrafast photoinduced local structural distortions of BiFeO3

    NASA Astrophysics Data System (ADS)

    Wen, Haidan; Sassi, Michel; Luo, Zhenlin; Adamo, Carolina; Schlom, Darrell G.; Rosso, Kevin M.; Zhang, Xiaoyi

    2015-10-01

    The interaction of light with materials is an intensively studied research forefront, in which the coupling of radiation energy to selective degrees of freedom offers contact-free tuning of functionalities on ultrafast time scales. Capturing the fundamental processes and understanding the mechanism of photoinduced structural rearrangement are essential to applications such as photo-active actuators and efficient photovoltaic devices. Using ultrafast x-ray absorption spectroscopy aided by density functional theory calculations, we reveal the local structural arrangement around the transition metal atom in a unit cell of the photoferroelectric archetype BiFeO3 film. The out-of-plane elongation of the unit cell is accompanied by the in-plane shrinkage with minimal change of interaxial lattice angles upon photoexcitation. This anisotropic elastic deformation of the unit cell is driven by localized electric field as a result of photoinduced charge separation, in contrast to a global lattice constant increase and lattice angle variations as a result of heating. The finding of a photoinduced elastic unit cell deformation elucidates a microscopic picture of photocarrier-mediated non-equilibrium processes in polar materials.

  9. Photoinduced magnetic force between nanostructures

    NASA Astrophysics Data System (ADS)

    Guclu, Caner; Tamma, Venkata Ananth; Wickramasinghe, Hemantha Kumar; Capolino, Filippo

    2015-12-01

    Photoinduced magnetic force between nanostructures, at optical frequencies, is investigated theoretically. Till now optical magnetic effects were not used in scanning probe microscopy because of the vanishing natural magnetism with increasing frequency. On the other hand, artificial magnetism in engineered nanostructures led to the development of measurable optical magnetism. Here two examples of nanoprobes that are able to generate strong magnetic dipolar fields at optical frequency are investigated: first, an ideal magnetically polarizable nanosphere and then a circular cluster of silver nanospheres that has a looplike collective plasmonic resonance equivalent to a magnetic dipole. Magnetic forces are evaluated based on nanostructure polarizabilities, i.e., induced magnetic dipoles, and magnetic-near field evaluations. As an initial assessment on the possibility of a magnetic nanoprobe to detect magnetic forces, we consider two identical magnetically polarizable nanoprobes and observe magnetic forces on the order of piconewtons, thereby bringing it within detection limits of conventional atomic force microscopes at ambient pressure and temperature. The detection of magnetic force is a promising method in studying optical magnetic transitions that can be the basis of innovative spectroscopy applications.

  10. Photoinduced toxicity of engineered nanomaterials

    NASA Astrophysics Data System (ADS)

    Jones, Philip Scott

    Engineered nanomaterials including metal, metal oxide and carbon based nanomaterials are extensively used in a wide variety of applications to the extent that their presence in the environment is expected to increase dramatically over the next century. These nanomaterials may be photodegraded by solar radiation and thereby release metal ions into the environment that can produce cytotoxic and genotoxic effects. Photoinduced toxicity experiments are performed exposing human lung epithelial carcinoma cells [H1650] to engineered semiconductor nanoparticles such as CdSe quantum dots and ZnO nanoparticles after exposure to 3, 6, and 9 hours of solar simulated radiation. Cytotoxicity and genotoxicity of the metal ions are evaluated using ZnSO4 and CdCl2 solutions for the MTT assay and Comet assay respectively. The objective of the dissertation is to obtain quantitative information about the environmental transformation of engineered nanomaterials and their mechanism of toxicity. This information is critical for addressing the environmental health and safety risks of engineered nanomaterials to workers, consumers and the environment.

  11. Acceleration of ventricular rate by amiodarone in atrial fibrillation associated with the Wolff-Parkinson-White syndrome

    PubMed Central

    Sheinman, Bryan D; Evans, Tom

    1982-01-01

    Amiodarone has proved to be a valuable drug in atrial fibrillation associated with the Wolff-Parkinson-White syndrome. When it was administered to a patient with this syndrome in atrial fibrillation, who had previously suffered an inferior myocardial infarction, the ventricular rate accelerated from 170 to 230 beats/minute. This unusual case emphasises the need for full electrophysiological assessment of patients with the Wolff-Parkinson-White syndrome for whom amiodarone treatment is being considered. Imagesp1000-a PMID:6812745

  12. Claisen thermally rearranged (CTR) polymers

    PubMed Central

    Tena, Alberto; Rangou, Sofia; Shishatskiy, Sergey; Filiz, Volkan; Abetz, Volker

    2016-01-01

    Thermally rearranged (TR) polymers, which are considered the next-generation of membrane materials because of their excellent transport properties and high thermal and chemical stability, are proven to have significant drawbacks because of the high temperature required for the rearrangement and low degree of conversion during this process. We demonstrate that using a [3,3]-sigmatropic rearrangement, the temperature required for the rearrangement of a solid glassy polymer was reduced by 200°C. Conversions of functionalized polyimide to polybenzoxazole of more than 97% were achieved. These highly mechanically stable polymers were almost five times more permeable and had more than two times higher degrees of conversion than the reference polymer treated under the same conditions. Properties of these second-generation TR polymers provide the possibility of preparing efficient polymer membranes in a form of, for example, thin-film composite membranes for various gas and liquid membrane separation applications. PMID:27482538

  13. Suppression of refractory arrhythmias by aprindine in patients with the Wolff-Parkinson-White syndrome.

    PubMed Central

    Reid, P R; Greene, H L; Varghese, P J

    1977-01-01

    Four patients with supraventricular tachycardia associated with the Wolff-Parkinson-White syndrome were refractory to conventional pharmacological therapy and received aprindine hydrochloride intravenously and orally. Electrophysiological studies disclosed that intravenous aprindine caused increased refractoriness and slowed conduction in the atria, atrioventricular node, ventricles, and accessory pathway. The ability to induce supraventricular tachycardia with timed atrial and ventricular premature stimuli was totally abolished in all 4 patients after intravenous aprindine. Oral aprindine therapy, twice daily thereafter, provided symptomatic relief of the supraventricular tachycardia without significant side effects. Aprindine is useful in the management of supraventricular tachycardia associated with Wolff-Parkinson-White and may offer significant advantages over currently available therapy. Images PMID:603737

  14. [Electrophysiological effects of chloroacetyl ajmaline in Wolff-Parkinson-White syndrome].

    PubMed

    Touboul, P; Gressard, A; Atallah, G; Chatelain, M T; Delahaye, J P

    1978-07-01

    The electrophysiological effects of chloro-acetyl-ajmaline in the Wolff-Parkinson-White syndrome have been studied in 7 patients after an intravenous dose of 1.5 mg/kg of the drug. Preexcitation was abolished in 3 cases, while 3 other subjects showed a slight increase in effective refractory period of the abnormal route of excitation (a mean of 13 ms). The possibility of bringing about a reciprocal rhythm was removed in one case out of two. During tachycardia, chloro-acetyl-ajmaline produced significant lengthening of the ventriculo-atrial conduction time (p less than 0.05). These results show the usefulness of chloro-acetyl-ajmaline in the control of the arrhythmias associated with the Wolff-Parkinson-White syndrome.

  15. Computational study of Wolff's law with trabecular architecture in the human proximal femur using topology optimization.

    PubMed

    Jang, In Gwun; Kim, Il Yong

    2008-08-07

    In the field of bone adaptation, it is believed that the morphology of bone is affected by its mechanical loads, and bone has self-optimizing capability; this phenomenon is well known as Wolff's law of the transformation of bone. In this paper, we simulated trabecular bone adaptation in the human proximal femur using topology optimization and quantitatively investigated the validity of Wolff's law. Topology optimization iteratively distributes material in a design domain producing optimal layout or configuration, and it has been widely and successfully used in many engineering fields. We used a two-dimensional micro-FE model with 50 microm pixel resolution to represent the full trabecular architecture in the proximal femur, and performed topology optimization to study the trabecular morphological changes under three loading cases in daily activities. The simulation results were compared to the actual trabecular architecture in previous experimental studies. We discovered that there are strong similarities in trabecular patterns between the computational results and observed data in the literature. The results showed that the strain energy distribution of the trabecular architecture became more uniform during the optimization; from the viewpoint of structural topology optimization, this bone morphology may be considered as an optimal structure. We also showed that the non-orthogonal intersections were constructed to support daily activity loadings in the sense of optimization, as opposed to Wolff's drawing.

  16. Comparative effects of ajmaline on intermittent bundle branch block and the Wolff-Parkinson-White syndrome.

    PubMed

    Chiale, P A; Przybylski, J; Halpern, M S; Lazzari, J O; Elizari, M V; Rosenbaum, M B

    1977-05-04

    Phase 4 or phase 3 block or both occurred in the His bundle branch system of 11 patients with intermittent bundle branch block and in the anomalous bundle of 6 of 46 patients with the Wolff-Parkinson-White syndrome (13%). Administration of a single dose of ajmaline (50 mg intravenously) in these patients caused a similar response: expansion of the range of phase 3 and phase 4 block at the expense of the intermediate normal conduction range and total interruption of conduction in the affected fascicle when the effect of the drug was maximal. The great similarity in physiologic behavior and pharmacologic response in these groups of patients suggests that the anomalous bundle was probably diseased or abnormal in the six patients with Wolff-Parkinson-White conduction. In addition, ajmaline caused the first appearance of phase 4 or phase 3 block, or both, but not total interruption of conduction in 26 of the 46 patients with Wolff-Parkinson-White conduction (56.5%). Ajmaline does not cause fascicular block in normal subjects; thus this finding suggests either that the anomalous bundle is diseased or that the safety margin for conduction in the anomalous bundle is much narrower than in the bundle branch system. The conduction-depressing action of ajmaline may be greater at relatively rapid or relatively slow rates of stimulation, and smaller or absent at intermediate rates.

  17. [Does patient age influence the indications for investigating asympatomatic Wolff-Parkinson-White syndrome?].

    PubMed

    Brembilla-Perrot, B; Holban, I; Houriez, P; Beurrier, D; Claudon, O; Vançon, A C

    2000-12-01

    Sudden death may be the presenting symptom of a Wolff-Parkinson-White syndrome. Electrophysiological investigation is the best method of identifying high risk cases. The aim of this study was to determine whether this investigation should be proposed to all patients, irrespective of age. Transoesophageal stimulation was performed in 85 asymptomatic patients with the Wolff-Parkinson-White syndrome. Of the 85 subjects, 13 were under 20 years of age, 30 under 30 years, 15 under 40 years, 16 under 50 years and 11 between 50 and 69 years of age. A protocol of incremental stimulation until 2nd degree AVB was attained and programmed atrial stimulation with one or two extrastimuli delivered on 2 paced cycles (600 and 400 ms) was used under basal conditions and with Isoprenaline. A malignant form of the condition was defined as the demonstration of two abnormalities: rapid conduction in the bundle of Kent (over 240/min) under basal conditions or over 300/min after Isoprenaline, and if it induced sustained atrial fibrillation (> 1 min). The results were: [table: see text] In conclusion, the number of malignant forms of the Wolff-Parkinson-White syndrome is exactly the same, irrespective of age. Elderly patients remain at risk of malignant WPW syndrome because of the increased incidence of atrial fibrillation. Therefore, the authors recommend systematic evaluation of this syndrome if the patient has an active life-style especially with regard to sporting activities.

  18. Immunoglobulin λ Gene Rearrangement Can Precede κ Gene Rearrangement

    DOE PAGES

    Berg, Jörg; Mcdowell, Mindy; Jäck, Hans-Martin; ...

    1990-01-01

    Imore » mmunoglobulin genes are generated during differentiation of B lymphocytes by joining gene segments. A mouse pre-B cell contains a functional immunoglobulin heavy-chain gene, but no light-chain gene. Although there is only one heavy-chain locus, there are two lightchain loci: κ and λ .It has been reported that κ loci in the germ-line configuration are never (in man) or very rarely (in the mouse) present in cells with functionally rearranged λ -chain genes. Two explanations have been proposed to explain this: (a) the ordered rearrangement theory, which postulates that light-chain gene rearrangement in the pre-B cell is first attempted at the κ locus, and that only upon failure to produce a functional κ chain is there an attempt to rearrange the λ locus; and (b) the stochastic theory, which postulates that rearrangement at the λ locus proceeds at a rate that is intrinsically much slower than that at the κ locus. We show here that λ -chain genes are generated whether or not the κ locus has lost its germ-line arrangement, a result that is compatible only with the stochastic theory.« less

  19. A Wolff in sheep's clothing: trabecular bone adaptation in response to changes in joint loading orientation.

    PubMed

    Barak, Meir M; Lieberman, Daniel E; Hublin, Jean-Jacques

    2011-12-01

    This study tests Wolff's law of trabecular bone adaptation by examining if induced changes in joint loading orientation cause corresponding adjustments in trabecular orientation. Two groups of sheep were exercised at a trot, 15 min/day for 34 days on an inclined (7°) or level (0°) treadmills. Incline trotting caused the sheep to extend their tarsal joints by 3-4.5° during peak loading (P<0.01) but has no effect on carpal joint angle (P=0.984). Additionally, tarsal joint angle in the incline group sheep were maintained more extended throughout the day using elevated platform shoes on their forelimbs. A third "sedentary group" group did not run but wore platform shoes throughout the day. As predicted by Wolff's law, trabecular orientation in the distal tibia (tarsal joint) were more obtuse by 2.7 to 4.3° in the incline group compared to the level group; trabecular orientation was not significantly different in the sedentary and level groups. In addition, trabecular orientations in the distal radius (carpal joint) of the sedentary, level and incline groups did not differ between groups, and were aligned almost parallel to the radius long axis, corresponding to the almost straight carpal joint angle at peak loading. Measurements of other trabecular bone parameters revealed additional responses to loading, including significantly higher bone volume fraction (BV/TV), Trabecular number (Tb.N) and trabecular thickness (Tb.Th), lower trabecular spacing (Tb.Sp), and less rod-shaped trabeculae (higher structure model index, SMI) in the exercised than sedentary sheep. Overall, these results demonstrate that trabecular bone dynamically adjusts and realigns itself in very precise relation to changes in peak loading direction, indicating that Wolff's law is not only accurate but also highly sensitive.

  20. A fetal Wolff-Parkinson-White syndrome diagnosed prenatally by magnetocardiography.

    PubMed

    Hosono, T; Chiba, Y; Shinto, M; Kandori, A; Tsukada, K

    2001-01-01

    We report a case of fetal Wolff-Parkinson-White (WPW) syndrome diagnosed prenatally by magnetocardiography (MCG). At 32 weeks' gestation, the fetus was diagnosed to have a paroxysmal supraventricular tachycardia by ultrasonography and direct fetal electrocardiogram (ECG). Transplacental fetal therapy by maternal oral administration of propranolol resolved the fetal tachyarrhythmia. Although the wave forms of the fetal MCG at 32 weeks' gestation were normal, the fetal MCG at 35 weeks' gestation showed a short PR interval and a long QRS complex duration with a delta wave, indicating WPW syndrome. The findings of the fetal MCG were confirmed by the postnatal ECG. MCG made the prenatal diagnosis of WPW syndrome possible.

  1. Asymptotic behavior and Denjoy-Wolff theorems for Hilbert metric nonexpansive maps

    NASA Astrophysics Data System (ADS)

    Lins, Brian C.

    We study the asymptotic behavior of fixed point free Hilbert metric nonexpansive maps on bounded convex domains. For such maps, we prove that the omega limit sets are contained in a convex subset of the boundary when the domain is either polyhedral or two dimensional. Similar results are obtained for several classes of positive operators defined on closed cones, including linear maps, affine linear maps, max-min operators, and reproduction-decimation operators. We discuss the relationship between these results and other Denjoy-Wolff type theorems. In particular, we investigate the interaction of nonexpansive maps with the horofunction boundary in the Hilbert geometry and in finite dimensional normed spaces.

  2. Photoinduced mass transport in azo compounds

    NASA Astrophysics Data System (ADS)

    Klismeta, K.; Teteris, J.; Aleksejeva, J.

    2013-12-01

    The photoinduced changes of optical properties in azobenzene containing compound thin films were studied under influence of polarized and non-polarized 532 nm laser light. Under influence of light azo compounds experience trans-cis isomerisation process, that can be observed in the absorbance spectrum of the sample. If the light is linearly polarized, molecules align perpendicularly to the electric field vector and as a result photoinduced dichroism and birefringence is obtained. If a known lateral polarization modulation of the light beam is present, mass transport of the azobenzene containing compound occurs. By measuring the surface relief with a profilometer the direction of mass transport can be determined. The studies of this work show that direct holographic recording of surface relief gratings can be used in optoelectronics, telecommunications and data storage.

  3. Coumarin-Induced DNA Ligation, Rearrangement to DNA Interstrand Crosslinks, and Photorelease of Coumarin Moiety.

    PubMed

    Sun, Huabing; Fan, Heli; Eom, Hyeyoung; Peng, Xiaohua

    2016-11-03

    Coumarin moieties react with thymine and cytosine in DNA by photoinduced [2+2] cycloaddition, which allows quantitative DNA interstrand crosslink (ICL) formation. Here, we report the application of coumarin analogues for DNA photoligation and the rearrangement of coumarin-induced ligation to ICL products. Both DNA sequences and the linker units at position 4 of the coumarin moieties affected coumarin-induced DNA photoligation. A flexible linker unit favored DNA ICL formation but led to inefficient photoligation, whereas coumarins without linker units greatly increased DNA photoligation efficiency. DNA photoligation induced by the coumarin moiety was photoswitchable. Ligation products were formed between coumarin and dT or dC upon 350 nm irradiation but reverted to the original single-stranded oligodeoxyribonucleotides (ODNs) upon 254 nm irradiation. Rearrangement of ligated ODNs into ICL products occurred during the switchable (350 nm/254 nm) processes. Additionally, photoinduced cleavage of coumarin 3 occurred with dC-3 cycloadducts upon 254 nm irradiation, which was confirmed by mass spectrometry analysis.

  4. Quantum pattern formation dynamics of photoinduced nucleation

    NASA Astrophysics Data System (ADS)

    Ishida, Kunio; Nasu, Keiichiro

    2008-06-01

    We study the dynamics of quantum pattern formation processes in molecular crystals which is concomitant with photoinduced nucleation. Since the nucleation process in coherent regime is driven by the nonadiabatic transition in each molecule followed by the propagation of phonons, it is necessary to take into account the quantum nature of both electrons and phonons in order to pursue the dynamics of the system. Therefore, we employ a model of localized electrons coupled with a quantized phonon mode and solve the time-dependent Schrödinger equation numerically. We found that there is a minimal size of clusters of excited molecules which triggers the photoinduced nucleation process; i.e., nucleation does not take place unless sufficient photoexcitation energy is concentrated within a narrow area of the system. We show that this result means that the spatial distribution of photoexcited molecules plays an important role in the nonlinearity of the dynamics and also in the optical properties observed in experiments. We calculate the conversion ratio, the rate of cluster formation, and correlation functions to reveal the dynamical properties of the pattern formation process; the initial dynamics of the photoinduced structural change is discussed from the viewpoint of pattern formation.

  5. Spinal Anaesthesia is Safe in a Patient with Wolff-Parkinson-White Syndrome Undergoing Evacuation of Molar Pregnancy

    PubMed Central

    Pujari, Vinayak S

    2016-01-01

    Wolff-Parkinson-White (WPW) syndrome is an uncommon cardiac condition where there is an abnormal band of atrial tissue connecting atria and ventricles which can electrically bypass atrioventricular node. The anaesthetic management in these patients is challenging as life threatening complications can occur perioperatively like paroxysmal supraventricular tachycardia and atrial fibrillation. Also, regional anaesthetic technique like subarachnoid block is a safe and cost effective alternative to general anaesthesia as it avoids polypharmacy. We report the successful anaesthetic management of Wolff Parkinson White syndrome in a primi with hydatiform mole posted for suction and evacuation. PMID:27042562

  6. [Treatment of junctional paroxysmal tachycardia, without patent Wolff-Parkinson-White syndrome, by sectioning an accessory Kent-His bundle].

    PubMed

    Slama, R; Attuel, P; Flammang, D; Coumel, P; Guiraudon, G

    1976-11-01

    The authors report the case of a patient suffering from a Bouveret's tachycardia without syndrome of Wolff-Parkinson-White. The analysis of the tachycardic spells however showed that during a reciprocal crisis, the circuit went through a left accessory ventriculo-atrial bundle, functioning only in the reverse direction. This accessory bundle was successfully cut by the surgeon, following the procedure of wide atrioventricular desinsertion as described by the authors of Duke University for the surgical treatment of the Wolff-Parkinson-White syndrome.

  7. The aging of Wolff's "law": ontogeny and responses to mechanical loading in cortical bone.

    PubMed

    Pearson, Osbjorn M; Lieberman, Daniel E

    2004-01-01

    The premise that bones grow and remodel throughout life to adapt to their mechanical environment is often called Wolff's law. Wolff's law, however, is not always true, and in fact comprises a variety of different processes that are best considered separately. Here we review the molecular and physiological mechanisms by which bone senses, transduces, and responds to mechanical loads, and the effects of aging processes on the relationship (if any) between cortical bone form and mechanical function. Experimental and comparative evidence suggests that cortical bone is primarily responsive to strain prior to sexual maturity, both in terms of the rate of new bone growth (modeling) as well as rates of turnover (Haversian remodeling). Rates of modeling and Haversian remodeling, however, vary greatly at different skeletal sites. In addition, there is no simple relationship between the orientation of loads in long bone diaphyses and their cross-sectional geometry. In combination, these data caution against assuming without testing adaptationist views about form-function relationships in order to infer adult activity patterns from skeletal features such as cross-sectional geometry, cortical bones density, and musculo-skeletal stress markers. Efforts to infer function from shape in the human skeleton should be based on biomechanical and developmental models that are experimentally tested and validated.

  8. [Fitness for sports of patients with Wolff-Parkinson-White syndrome].

    PubMed

    Montgermont, P; Adams, C; Heulin, A; Vacheron, A

    1987-06-01

    The fitness of patients with Wolff-Parkinson-White syndrome to indulge in sporting activities is a practical cardiology problem. The major risk is sudden death due to atrial fibrillation deteriorating to ventricular fibrillation. This risk is small or even theoretical, but signing a fitness certificate engages the clinician's responsibility. Non invasive complementary examinations are useful. Echocardiography may detect a heart disease that would preclude any sport. Exercise tests explore the behaviour of the accessory pathway and rarely trigger off arrhythmias. Holter recordings mainly investigate disorders of the atrial rhythm. The decision concerning fitness may be based on clinical symptoms. Exercise-induced tachycardia is a classical contra-indication to competitive sports. In patients whose tachycardia is unrelated to exercise, fitness may be discussed according to the results of exercise tests and of the electrophysiological study. A refractory period which would be considered as rather prolonged at rest does not protect against fast ventricular rate during passage to atrial fibrillation. If pre-excitation disappears during the exercise test in an asymptomatic patient, then competitive sports can be authorized without limitations. If not, only surgical excision or fulguration would provide full protection against a potentially dangerous fibrillation. It is concluded that Wolff-Parkinson-White syndrome contra-indicates competitive sports in most cases. Games played outside competitions remain possible in the absence of symptoms or when arrhythmias are well controlled by medical treatment.

  9. [Is the transesophageal approach preferable to endocavitary approach in the evaluation of Wolff-Parkinson-White syndrome?].

    PubMed

    Brembilla-Perrot, B; Beurrier, D

    1995-03-01

    Now that the radical treatment of the Wolff-Parkinson-White syndrome is established, it is essential to evaluate the prognosis of this condition accurately. Initiation of atrial fibrillation is one of the factors which influence the prognosis. The aim of this study was to compare the results of electrophysiological studies performed by the endocavitary and transoesophageal approaches in the measurement of the initiation of atrial fibrillation. Twenty-six patients with a patent Wolff-Parkinson-White syndrome were studied by the two methods with a similar protocol: incremental atrial pacing to the Wenckebach point, programmed atrial stimulation using up to two extrastimuli, repeated with an infusion of 20 to 30 ug of isoproterenol. Sixteen patients had reciprocating nodal tachycardia or were asymptomatic (group I) and the other 10 had spontaneous atrial fibrillation (group II). In group I, atrial fibrillation was induced in 9 cases (56%) by the endocavitary and in two cases (12.5%) by the transoesophageal method. In group II, spontaneous atrial fibrillation was reproduced in all cases by the endocavitary and transoesophageal protocols. None of the patients in group I developed atrial fibrillation during follow-up (average 2 years +/- 9 months). The authors observe that all spontaneous atrial fibrillation of the Wolff-Parkinson-White syndrome can be triggered by oesophageal stimulation. The prevalence of atrial fibrillation was overestimated by endocavitary studies in asymptomatic or paucisymptomatic patients. The assessment of atrial vulnerability of a Wolff-Parkinson-White syndrome may therefore be performed by transoesophageal electro-physiological studies.

  10. Sensitivity as a Privileged Predictor of Attachment: A Second Perspective of De Wolff and van IJzendoorn's Meta-Analysis

    ERIC Educational Resources Information Center

    Nievar, M. Angela; Becker, Betsy Jane

    2004-01-01

    This secondary analysis of De Wolff and van IJzendoorn's (1997) meta-analysis of maternal behavior and attachment reexamined their conclusion that sensitivity was not a preferred predictor of attachment security. The meta-analysis included 66 studies with 123 effect sizes sorted through a combination of personal choice and homogeneity analysis…

  11. Photoinduced heterostructure in a vanadium dioxide film

    NASA Astrophysics Data System (ADS)

    Semenov, A. L.

    2017-02-01

    A photoinduced semiconductor-metal phase transition that occurs in a surface layer of vanadium dioxide film on an aluminum substrate within the time Δ t < 1 ps has been studied theoretically. A nonthermal mechanism of the development of instability has been considered. It has been shown that a heterophase structure containing metallic and semiconductor layers is formed in the VO2 film. The phase transition time τ has been calculated as a function of the distance z from the film surface. Comparison with the experiment has been carried out.

  12. [Wolff-Parkinson-White syndrome after 50 yars of age. Clinical and electrophysiological data].

    PubMed

    Lévy, S; Borde, C; Dupon, J; Bémurat, M; Gérard, R; Bricaud, H

    1980-07-01

    The Wolff-Parkinson-White syndrome is usually observed in young people and is much rarer in patients over 50 years old. This fact may be explained by the demise of a certain number of patients before the age of 50 and/or a change in the clinical features of the syndrome with age and/or of the electrophysiological properties of the normal and accessory conduction pathways. To test the latter hypothesis, the clinical and electrophysiological data of 15 patients over 50 years old with the Wolff-Parkinson-White syndrome (Group I) were compared with that of 10 patients under 30 years old with the same syndrome (Group II). The same protocol of electrophysiological investigation was used in both groups of patients. The results showed a significant difference (p < 0.001) between the two groups in the incidence of associated cardiac disease. This was more common in Group I (1 4 out of 15 patients) than in Group II (2 out of 10 patients). The cardiothoracic ratio was significantly higher in Group I (p < 0.01). The two groups also differed in the age at which tachycardia first occured. 9 out of 11 patients in Group I only had symptoms after thirty years. On the other hand, there was no significant difference in the types of tachycardia and the frequency of attacks. There was no significant difference in QRS, PR, AH, HV intervals, in the ventriculo-atrial conduction time and the effective refractory periods of the atrium, right ventricle or atrio-ventricular node. There was no significant difference in the anterograde and retrograde refractory periods of the accessory pathways between the two groups. Reciprocating tachycardia, initiated by electrical stimulation in 7 patients in Group I and 6 patients in Group II, was conducted anterogradely to the ventricles through the normal pathway and retrogradely to the atria through the the accessory pathway. This study suggest that age-related changes in the electrophysiological properties of the accessory are not an important

  13. Kinetics of a photoinduced NH tautomerism of free-base porphyrins in crystalline matrices at low temperatures: Computer simulations and experiment

    NASA Astrophysics Data System (ADS)

    Stanishevsky, I. V.; Solovyov, K. N.

    2004-03-01

    Photoinduced NH tautomerism, along with the reaction pathways of phototautomerization in tetrabenzoporphin and porphin free bases in n-octane polycrystalline matrices at 77 K, is studied by simulation of kinetic processes and their experimental observation. The simulation of the processes is performed by the numerical solution of the system of kinetic equations describing the populations of electronic levels and transitions between them. Kinetic dependences are obtained by measuring the perturbation of stationary fluorescence of one component of the 0-0 doublet origin upon pulsed selective photoexcitation of the other component. For two tautomeric forms related by the reversibility of the photochemical reaction, under the assumption of synchronism of the NH rearrangement, (i) analytical solutions governing the reaction rate are found, (ii) a method of measuring the rate constants of the proton rearrangement is suggested and the constants themselves are estimated, and (iii) direct evidence of the participation of T 1 levels in the photochemical reaction is obtained. With the aid of numerical simulations, the specific features of kinetic manifestation of an asynchronous mechanism of the photoinduced NH rearrangement are studied.

  14. DNA Rearrangements through Spatial Graphs

    NASA Astrophysics Data System (ADS)

    Jonoska, Nataša; Saito, Masahico

    The paper is a short overview of a recent model of homologous DNA recombination events guided by RNA templates that have been observed in certain species of ciliates. This model uses spatial graphs to describe DNA rearrangements and show how gene recombination can be modeled as topological braiding of the DNA. We show that a graph structure, which we refer to as an assembly graph, containing only 1- and 4-valent rigid vertices can provide a physical representation of the DNA at the time of recombination. With this representation, 4-valent vertices correspond to the alignment of the recombination sites, and we model the actual recombination event as smoothing of these vertices.

  15. Effect of exercise on ventricular response to atrial fibrillation in Wolff-Parkinson-White syndrome.

    PubMed Central

    Crick, J C; Davies, D W; Holt, P; Curry, P V; Sowton, E

    1985-01-01

    Ten patients with Wolff-Parkinson-White syndrome underwent cardiac electrophysiological study extended to include the induction of atrial fibrillation at maximum exercise in the upright position. This was performed using a new temporary bipolar lead with a helical active fixation tip for atrial pacing. The highest rate of atrioventricular conduction via the accessory pathway was greater during exercise than at rest in all 10 patients (mean increase 28%). In three cases the resulting ventricular rate exceeded 300 beats/min, but no patient had severe symptoms or ventricular arrhythmias. The exercise induced enhancement of accessory pathway conduction may significantly but unpredictably affect the risk from spontaneous atrial fibrillation especially in patients with coronary artery disease or in those taking antiarrhythmic drugs. The test procedure was sufficiently simple and well tolerated to be included in our routine electrophysiological investigation. PMID:4015920

  16. [Wolff-Parkinson-White syndrome and longitudinal dissociation of the atrioventricular node. Anatomical and electrophysiological correlates].

    PubMed

    Brechenmacher, C; Fauchier, J P; James, T N

    1981-07-01

    A 58 year old man who died of metastatic carcinoma had undergone electrophysiological investigation 4 years previously for a Wolff-Parkinson-White syndrome (Rosenbaum Type A, Frank and Boineau Type IV) associated with supraventricular tachycardia (SVT) at 180/mn, atrial fibrillation and flutter and slow junctional (or low atrial) rhythm at 70-80/mn. Atrial extrasystoles or appropriate atrial stimulation not only induced and terminated the SVT but also the junctional rhythm and allowed passage from one arrhythmia to another. These studies showed the presence of a left lateral Kent bundle responsible for orthodromic SVT with retrograde conduction through the accessory pathway, and suggested that the junctional rhythm might be due to longitudinal dissociation of the AV node. Autopsy findings confirmed the presence of the left posterolateral Kent bundle in an almost horizontal position, parallel to the mitral annulus (it might therefore have escaped eventual surgical section) and the longitudinal dissociation of the AV node.

  17. [Polymorphic atrial tachycardia and Wolff-Parkinson-White syndrome in a newborn infant].

    PubMed

    Chantepie, A; Ramponi, N; Vaillant, M C; Laugier, J; Raynaud, P; Fauchier, J P

    1986-08-01

    The authors report a case of polymorphic supraventricular tachycardia in a premature neonate born at 33 weeks by caesarean section because of foeto-placental insufficiency and hydramnios due to foetal tachycardia diagnosed in utero. This arrhythmia was of interest because of the association of chaotic atrial tachycardia and the Wolff-Parkinson-White syndrome (WPW), which has rarely been described in the neonate. The mechanism of atrial tachycardia in the WPW syndrome is variable. In our case, there was retrograde atrial activation by the accessory pathway with atrial desynchronisation aided by left atrial dilatation. Digoxin, an effective anti arrhythmic agent in neonatal tachycardia, should not be used in cases of atrial tachycardia associated with ventricular preexcitation because of the risk of dangerous ventricular tachycardia.

  18. Wolff-type embedding algorithms for general nonlinear σ-models

    NASA Astrophysics Data System (ADS)

    Caracciolo, Sergio; Edwards, Robert G.; Pelissetto, Andrea; Sokal, Alan D.

    1993-08-01

    We study a class of Monte Carlo algorithms for the nonlinear σ-model, based on A Wolff-type embedding of Ising spins into the target manifold M. We argue heuristically that, at least for an asymptotically free model, such an algorithm can have a dynamic critical exponent z « 2 only if the embedding is based on an (involutive) isometry of M whose fixed-point manifold has codimension 1. Such an isometry exist only if the manifold is a discrete quotient of a product of spheres. Numerical simulations of the idealized codimension-2 algorithm for the two-dimensional O(4)-symmetric σ-model yield z int, M2 = 1.5±0.5 (sujective 68% confidence interval), in agreement with our heuristic argument.

  19. Photoinduced Force Mapping of Plasmonic Nanostructures.

    PubMed

    Tumkur, Thejaswi U; Yang, Xiao; Cerjan, Benjamin; Halas, Naomi J; Nordlander, Peter; Thomann, Isabell

    2016-12-14

    The ability to image the optical near-fields of nanoscale structures, map their morphology, and concurrently obtain spectroscopic information, all with high spatiotemporal resolution, is a highly sought-after technique in nanophotonics. As a step toward this goal, we demonstrate the mapping of electromagnetic forces between a nanoscale tip and an optically excited sample consisting of plasmonic nanostructures with an imaging platform based on atomic force microscopy. We present the first detailed joint experimental-theoretical study of this type of photoinduced force microscopy. We show that the enhancement of near-field optical forces in gold disk dimers and nanorods follows the expected plasmonic field enhancements with strong polarization sensitivity. We then introduce a new way to evaluate optically induced tip-sample forces by simulating realistic geometries of the tip and sample. We decompose the calculated forces into in-plane and out-of-plane components and compare the calculated and measured force enhancements in the fabricated plasmonic structures. Finally, we show the usefulness of photoinduced force mapping for characterizing the heterogeneity of near-field enhancements in precisely e-beam fabricated nominally alike nanostructures - a capability of widespread interest for precise nanomanufacturing, SERS, and photocatalysis applications.

  20. Nanoscale chemical imaging by photoinduced force microscopy

    PubMed Central

    Nowak, Derek; Morrison, William; Wickramasinghe, H. Kumar; Jahng, Junghoon; Potma, Eric; Wan, Lei; Ruiz, Ricardo; Albrecht, Thomas R.; Schmidt, Kristin; Frommer, Jane; Sanders, Daniel P.; Park, Sung

    2016-01-01

    Correlating spatial chemical information with the morphology of closely packed nanostructures remains a challenge for the scientific community. For example, supramolecular self-assembly, which provides a powerful and low-cost way to create nanoscale patterns and engineered nanostructures, is not easily interrogated in real space via existing nondestructive techniques based on optics or electrons. A novel scanning probe technique called infrared photoinduced force microscopy (IR PiFM) directly measures the photoinduced polarizability of the sample in the near field by detecting the time-integrated force between the tip and the sample. By imaging at multiple IR wavelengths corresponding to absorption peaks of different chemical species, PiFM has demonstrated the ability to spatially map nm-scale patterns of the individual chemical components of two different types of self-assembled block copolymer films. With chemical-specific nanometer-scale imaging, PiFM provides a powerful new analytical method for deepening our understanding of nanomaterials. PMID:27051870

  1. Optimal Arrangement of Components Via Pairwise Rearrangements.

    DTIC Science & Technology

    1987-10-01

    reliability function under component pairwise rearrangement. They use this property to find the optimal component arrangement. Worked examples illustrate the methods proposed. Keywords: Optimization; Permutations; Nodes.

  2. Integrin activation and structural rearrangement.

    PubMed

    Takagi, Junichi; Springer, Timothy A

    2002-08-01

    Among adhesion receptor families, integrins are particularly important in biological processes that require rapid modulation of adhesion and de-adhesion. Activation on a timescale of < 1 s of beta2 integrins on leukocytes and beta3 integrins on platelets enables deposition of these cells at sites of inflammation or vessel wall injury. Recent crystal, nuclear magnetic resonance (NMR), and electron microscope (EM) structures of integrins and their domains lead to a unifying mechanism of activation for both integrins that contain and those that lack an inserted (I) domain. The I domain adopts two alternative conformations, termed open and closed. In striking similarity to signaling G-proteins, rearrangement of a Mg2+-binding site is linked to large conformational movements in distant backbone regions. Mutations that stabilize a particular conformation show that the open conformation has high affinity for ligand, whereas the closed conformation has low affinity. Movement of the C-terminal alpha-helix 10 A down the side of the domain in the open conformation is sufficient to increase affinity at the distal ligand-binding site 9,000-fold. This C-terminal "bell-rope" provides a mechanism for linkage to conformational movements in other domains. Recent structures and functional studies reveal interactions between beta-propeller, I, and I-like domains in the integrin headpiece, and a critical role for integrin epidermal growth factor (EGF) domains in the stalk region. The headpiece of the integrin faces down towards the membrane in the inactive conformation, and extends upward in a "switchblade"-like opening upon activation. These long-range structural rearrangements of the entire integrin molecule involving interdomain contacts appear closely linked to conformational changes within the I and I-like domains, which result in increased affinity and competence for ligand binding.

  3. Photoinduced Fusion of Lipid Bilayer Membranes.

    PubMed

    Suzuki, Yui; Nagai, Ken H; Zinchenko, Anatoly; Hamada, Tsutomu

    2017-03-14

    We have developed a novel system for photocontrol of the fusion of lipid vesicles through the use of a photosensitive surfactant containing an azobenzene moiety (AzoTAB). Real-time microscopic observations clarified a change in both the surface area and internal volume of vesicles during fusion. We also determined the optimal cholesterol concentrations and temperature for inducing fusion. The mechanism of fusion can be attributed to a change in membrane tension, which is caused by the solubilization of lipids through the isomerization of AzoTAB. We used a micropipet technique to estimate membrane tension and discuss the mechanism of fusion in terms of membrane elastic energy. The obtained results regarding this novel photoinduced fusion could lead to a better understanding of the mechanism of membrane fusion in living cells and may also see wider applications, such as in drug delivery and biomimetic material design.

  4. Photo-induced electron transfer method

    DOEpatents

    Wohlgemuth, R.; Calvin, M.

    1984-01-24

    The efficiency of photo-induced electron transfer reactions is increased and the back transfer of electrons in such reactions is greatly reduced when a photo-sensitizer zinc porphyrin-surfactant and an electron donor manganese porphyrin-surfactant are admixed into phospholipid membranes. The phospholipids comprising said membranes are selected from phospholipids whose head portions are negatively charged. Said membranes are contacted with an aqueous medium in which an essentially neutral viologen electron acceptor is admixed. Catalysts capable of transferring electrons from reduced viologen electron acceptor to hydrogen to produce elemental hydrogen are also included in the aqueous medium. An oxidizable olefin is also admixed in the phospholipid for the purpose of combining with oxygen that coordinates with oxidized electron donor manganese porphyrin-surfactant.

  5. Photo-induced electron transfer method

    DOEpatents

    Wohlgemuth, Roland; Calvin, Melvin

    1984-01-01

    The efficiency of photo-induced electron transfer reactions is increased and the back transfer of electrons in such reactions is greatly reduced when a photo-sensitizer zinc porphyrin-surfactant and an electron donor manganese porphyrin-surfactant are admixed into phospho-lipid membranes. The phospholipids comprising said membranes are selected from phospholipids whose head portions are negatively charged. Said membranes are contacted with an aqueous medium in which an essentially neutral viologen electron acceptor is admixed. Catalysts capable of transfering electrons from reduced viologen electron acceptor to hydrogen to produce elemental hydrogen are also included in the aqueous medium. An oxidizable olefin is also admixed in the phospholipid for the purpose of combining with oxygen that coordinates with oxidized electron donor manganese porphyrin-surfactant.

  6. Photoinduced decomposition of trichloroethylene in soil components

    SciTech Connect

    Tao, T.; Yang, J.J.; Maciel, G.E.

    1999-01-01

    The photoinduced decomposition of trichloroethylene adsorbed on Ca-montmorillonite by long-wavelength UV irradiation has been studied in a quartz tube open to air or through which air or oxygen is passed. Solid-sample and liquid-solution NMR techniques were used to identify apparent products or intermediates of the photodecomposition. Dichloroacetic acid was identified as a major organic product/intermediate; substantial amounts of pentachloroethane and trichloroacetic acid were also identified. The formation of CO{sub 2} was characterized quantitatively by wet chemical analysis. About 40% and 57%, respectively, of the total carbon of trichloroethylene was converted to carbon dioxide in air and O{sub 2} environments over a period of 16 days. Phosgene and HCl were also detected. The photodecomposition of trichloroethylene adsorbed on whole soil, on Zn{sup 2+}-exchanged and Cu{sup 2+}-exchanged montmorillonites, on kaolinite, and on silica gel was also examined in less detail; qualitatively, the conversion of trichloroethylene to dichloroacetic acid in a 48-h period occurred with the following order of decreasing efficiencies: Zn{sup 2+}-montmorillonite > silica gel > kaolinite > Ca{sup 2+}-montmorillonite > whole soil > Cu{sup 2+}-montmorillonite. These results show that the photoinduced decomposition of adsorbed trichloroethylene occurs on a variety of adsorbents, generating products and intermediates that are similar to what have been reported previously for TiO{sub 2}-based photodecomposition but with much longer time scales. These conversions can, therefore, be expected to occur in sunlight at the air-soil interface.

  7. Microwave accelerated aza-Claisen rearrangement.

    PubMed

    Gajdosíková, Eva; Martinková, Miroslava; Gonda, Jozef; Conka, Patrik

    2008-11-14

    A study of microwave-induced and standard thermal Overman rearrangement of selected allylic trichloroacetimidates 1a-1f, 6-8 to the corresponding acetamides 2a-2f, 9-11 is reported. The microwave-assisted rearrangement of trifluoroacetimidate 13 is also described. Using this methodology, an efficient access to versatile allylic trihaloacetamides building synthons was established.

  8. Review of the photo-induced toxicity of environmental contaminants.

    PubMed

    Roberts, Aaron P; Alloy, Matthew M; Oris, James T

    2017-01-01

    Solar radiation is a vital component of ecosystem function. However, sunlight can also interact with certain xenobiotic compounds in a phenomenon known as photo-induced, photo-enhanced, photo-activated, or photo-toxicity. This phenomenon broadly refers to an interaction between a chemical and sunlight resulting in increased toxicity. Because most aquatic ecosystems receive some amount of sunlight, co-exposure to xenobiotic chemicals and solar radiation is likely to occur in the environment, and photo-induced toxicity may be an important factor impacting aquatic ecosystems. However, photo-induced toxicity is not likely to be relevant in all aquatic systems or exposure scenarios due to variation in important ecological factors as well as physiological adaptations of the species that reside there. Here, we provide an updated review of the state of the science of photo-induced toxicity in aquatic ecosystems.

  9. Rearrangements of organic peroxides and related processes

    PubMed Central

    Yaremenko, Ivan A; Vil’, Vera A; Demchuk, Dmitry V

    2016-01-01

    Summary This review is the first to collate and summarize main data on named and unnamed rearrangement reactions of peroxides. It should be noted, that in the chemistry of peroxides two types of processes are considered under the term rearrangements. These are conventional rearrangements occurring with the retention of the molecular weight and transformations of one of the peroxide moieties after O–O-bond cleavage. Detailed information about the Baeyer−Villiger, Criegee, Hock, Kornblum−DeLaMare, Dakin, Elbs, Schenck, Smith, Wieland, and Story reactions is given. Unnamed rearrangements of organic peroxides and related processes are also analyzed. The rearrangements and related processes of important natural and synthetic peroxides are discussed separately. PMID:27559418

  10. Rearrangements of organic peroxides and related processes.

    PubMed

    Yaremenko, Ivan A; Vil', Vera A; Demchuk, Dmitry V; Terent'ev, Alexander O

    2016-01-01

    This review is the first to collate and summarize main data on named and unnamed rearrangement reactions of peroxides. It should be noted, that in the chemistry of peroxides two types of processes are considered under the term rearrangements. These are conventional rearrangements occurring with the retention of the molecular weight and transformations of one of the peroxide moieties after O-O-bond cleavage. Detailed information about the Baeyer-Villiger, Criegee, Hock, Kornblum-DeLaMare, Dakin, Elbs, Schenck, Smith, Wieland, and Story reactions is given. Unnamed rearrangements of organic peroxides and related processes are also analyzed. The rearrangements and related processes of important natural and synthetic peroxides are discussed separately.

  11. [Association of Wolff-Parkinson-White syndrome with isolated non-compaction of the left ventricle: a case report].

    PubMed

    Brembilla-Perrot, B; Codreanu, A; Marie, P Y; Beurrier, D; Husson, J L; Hutin, O; Pruna, A; Yangni N'Da, O; Ernst, Y; Bosser, G

    2006-06-01

    The Wolff-Parkinson-White syndrome (WPW) may be associated with a number of cardiac pathologies, especially congenital disease, in 7.5 to 17% of cases. The authors report a rare association of the WPW syndrome with two Kent bundles, right and left septal, with non-compaction of the left ventricle in a 52 year old man. This was a chance finding during systematic echocardiography after ablation, and confirmed by cardiac MRI. The patient was asymptomatic.

  12. Photoinduced nanocomposites—creation, modification, linear and nonlinear optical properties

    NASA Astrophysics Data System (ADS)

    Bityurin, N.; Alexandrov, A.; Afanasiev, A.; Agareva, N.; Pikulin, A.; Sapogova, N.; Soustov, L.; Salomatina, E.; Gorshkova, E.; Tsverova, N.; Smirnova, L.

    2013-07-01

    UV irradiation of materials consisting of a polymer matrix that possesses precursors of noble metals followed by annealing results in creation of metal nanoparticles within the irradiated domains. Such photoinduced nanocomposites are promising for photonics applications due to the strong alteration of their optical properties compared to initial nonirradiated materials. We report our results on the synthesis and investigation of two kinds of these materials: (a) Photoinduced Au nanocomposites based on PMMA matrices, including bulk materials prepared by means of the polymerization technique;

  13. Photoinduced electro-optics measurements of biosilica transformation to cristobalite

    SciTech Connect

    Fuchs, Ido; Aluma, Yaniv; Ilan, Micha; Kityk, Iwan; Mastai, Yitzhak

    2015-03-15

    In this paper we studied the photoinduced electro optics effects in the thermal transformation process of biosilica to cristobalite, at a relatively low temperature and ambient pressure. This process was characterized by a variety of standards techniques with emphasis on linear electro optic effect measurements. Overall we demonstrated that photoinduced electro optics measurements are very sensitive to the transformation from amorphous structure of silica in the natural sponge samples to laminar string morphology of cristobalite. With this technique we could probe the change in the samples chirality from achiral bio silica to chiral cristobalite structure. Furthermore it is shown that natural biosilica have photoinduced linear electro optics respond indicating the chiral natural of biosilica. - Graphical abstract: The phase transformation of biosilica from marine sponges to Cristobalite under thermal treatment was investigated using photoinduced electro optics measurements. The figure shows the changes of the electro-optic coefficient of cristobalite and biosilica. - Highlights: • We examine phase transformation of biosilica. • We report transition from amorphous biosilica to crystalline Cristobalite. • Biosilica transformation to Cristobalite at temperature of 850 °C. • Biosilica transformation is studied with photoinduced measurements. • We examine changes in the photoinduced linear electro optics properties.

  14. Diverse mutational mechanisms cause pathogenic subtelomeric rearrangements

    PubMed Central

    Luo, Yue; Hermetz, Karen E.; Jackson, Jodi M.; Mulle, Jennifer G.; Dodd, Anne; Tsuchiya, Karen D.; Ballif, Blake C.; Shaffer, Lisa G.; Cody, Jannine D.; Ledbetter, David H.; Martin, Christa L.; Rudd, M. Katharine

    2011-01-01

    Chromosome rearrangements are a significant cause of intellectual disability and birth defects. Subtelomeric rearrangements, including deletions, duplications and translocations of chromosome ends, were first discovered over 40 years ago and are now recognized as being responsible for several genetic syndromes. Unlike the deletions and duplications that cause some genomic disorders, subtelomeric rearrangements do not typically have recurrent breakpoints and involve many different chromosome ends. To capture the molecular mechanisms responsible for this heterogeneous class of chromosome abnormality, we coupled high-resolution array CGH with breakpoint junction sequencing of a diverse collection of subtelomeric rearrangements. We analyzed 102 breakpoints corresponding to 78 rearrangements involving 28 chromosome ends. Sequencing 21 breakpoint junctions revealed signatures of non-homologous end-joining, non-allelic homologous recombination between interspersed repeats and DNA replication processes. Thus, subtelomeric rearrangements arise from diverse mutational mechanisms. In addition, we find hotspots of subtelomeric breakage at the end of chromosomes 9q and 22q; these sites may correspond to genomic regions that are particularly susceptible to double-strand breaks. Finally, fine-mapping the smallest subtelomeric rearrangements has narrowed the critical regions for some chromosomal disorders. PMID:21729882

  15. Reversibility of cell surface label rearrangement

    PubMed Central

    1976-01-01

    Cell surface labeling can cause rearrangements of randomly distributed membrane components. Removal of the label bound to the cell surface allows the membrane components to return to their original random distribution, demonstrating that label is necessary to maintain as well as to induce rearrangements. With scanning electron microscopy, the rearrangement of concanavalin A (con A) and ricin binding sites on LA-9 cells has been followed by means of hemocyanin, a visual label. The removal of con A from its binding sites at the cell surface with alpha- methyl mannoside, and the return of these sites to their original distribution are also followed in this manner. There are labeling differences with con A and ricin. Under some conditions, however, the same rearrangements are seen with both lectins. The disappearance of labeled sites from areas of ruffling activity is a major feature of the rearrangements seen. Both this ruffling activity and the rearrangement of label are sensitive to cytochalasin B, and ruffling activity, perhaps along with other cytochalasin-sensitive structure, may play a role in the rearrangements of labeled sites. PMID:1025154

  16. Lateral gene transfer, rearrangement, reconciliation

    PubMed Central

    2013-01-01

    Background Models of ancestral gene order reconstruction have progressively integrated different evolutionary patterns and processes such as unequal gene content, gene duplications, and implicitly sequence evolution via reconciled gene trees. These models have so far ignored lateral gene transfer, even though in unicellular organisms it can have an important confounding effect, and can be a rich source of information on the function of genes through the detection of transfers of clusters of genes. Result We report an algorithm together with its implementation, DeCoLT, that reconstructs ancestral genome organization based on reconciled gene trees which summarize information on sequence evolution, gene origination, duplication, loss, and lateral transfer. DeCoLT optimizes in polynomial time on the number of rearrangements, computed as the number of gains and breakages of adjacencies between pairs of genes. We apply DeCoLT to 1099 gene families from 36 cyanobacteria genomes. Conclusion DeCoLT is able to reconstruct adjacencies in 35 ancestral bacterial genomes with a thousand gene families in a few hours, and detects clusters of co-transferred genes. DeCoLT may also be used with any relationship between genes instead of adjacencies, to reconstruct ancestral interactions, functions or complexes. Availability http://pbil.univ-lyon1.fr/software/DeCoLT/ PMID:24564205

  17. Existence of automaticity in anomalous bundle of Wolff-Parkinson-White syndrome.

    PubMed Central

    Przybylski, J; Chiale, P A; Halpern, M S; Lázzari, J O; Elizari, M V; Rosenbaum, M B

    1978-01-01

    Escape beats probably arising from the anomalous bundle were documented in 2 patients with the Wolff-Parkinson-White (WPW) syndrome. A third patient, in whom complete AV block developed both in the anomalous bundle and the normal pathway, showed the occurrence of escape beats (an escape-bigeminy pattern), as well as a regular idioventricular rhythm arising from the anomalous bundle. Phase 4 block in the anomalous bundle occurred in 7 other patients, in 4 of them spontaneously and in 3 only after the administration of ajmaline or amiodarone. Only 4 of 14 fully investigated patients (out of a total number of 23) showed absence of both escape beats and phase 4 block. The escape beats were considered as direct evidence, and the phase 4 block as indirect evidence, for the existence of automaticity in the anomalous bundle. Such evidence supports the view that the anomalous bundle, like the His bundle-branch system, may be composed of specialised tissue endowed with the property of automaticity. PMID:656241

  18. Trabecular bone of precocials at birth; Are they prepared to run for the wolf(f)?

    PubMed Central

    Wolschrijn, Claudia F.; van Vilsteren, Anouk A.M.; van Rietbergen, Bert; van Weeren, P. René

    2016-01-01

    ABSTRACT Bone is a dynamic tissue adapting to loading according to “Wolff's law of bone adaptation.” During very early life, however, such a mechanism may not be adequate enough to adapt to the dramatic change in environmental challenges in precocial species. Their neonates are required to stand and walk within hours after birth, in contrast to altricial animals that have much more time to adapt from the intrauterine environment to the outside world. In this study, trabecular bone parameters of the talus and sagittal ridge of the tibia from stillborn but full‐term precocials (calves and foals) were analyzed by micro‐CT imaging in order to identify possible anticipatory mechanisms to loading. Calculated average bone volume fraction in the Shetland pony (49–74%) was significantly higher compared to Warmblood foals (28–51%). Bovine trabecular bone was characterized by a low average bone volume fraction (22–28%), however, more directional anisotropy was found. It is concluded that anticipatory strategies in skeletal development exist in precocial species, which differ per species and are most likely related to anatomical differences in joint geometry and related loading patterns. The underlying regulatory mechanisms are still unknown, but they may be based on a genetic blueprint for the development of bone. More knowledge, both about a possible blueprint and its regulation, will be helpful in understanding developmental bone and joint diseases. J. Morphol. 277:948–956, 2016. © 2016 Wiley Periodicals, Inc. PMID:27098190

  19. Atrial pacing at multiple sites in the Wolff-Parkinson-White syndrome.

    PubMed Central

    Denes, P; Wyndham, C R; Amat-y-Leon, F; Wu, D; Dhingra, R C; Miller, R H; Rosen, K M

    1977-01-01

    Atrial pacing at multiple sites was used in an attempt to predict the site of pre-excitation in 5 patients with Wolff-Parkinson-White syndrome with 5 different anomalous pathway locations (right anterior, right posterior, septal, left posterior, and left lateral). At least 3 atrial pacing sites were tested in each patient. Pacing sites tested included high right atrium, low lateral right atrium, low septal right atrium, proximal coronary sinus, and distal coronary sinus. Atrial stimulation sites with shortest and longest stimulus-delta intervals could be identified in each patient, the shortest stimulus-delta interval in each case ranging from 60 to 80 ms. The difference between the shortest and longest stimulus-delta interval in each case ranged from 60 to 110 ms. It was suggested that the site with the shortest stimulus-delta interval corresponded to a site close to the atrial insertion of the anomalous pathway. This hypothesis was confirmed in all cases (3 with epicardial mapping and 2 with retrograde atrial activation data). In conclusion, atrial pacing at multiple sites is helpful in predicting the site of anterogradely conducting anomalous pathways, and appears particularly useful for differentiation of right posterior, left posterior, and septal pre-excitation. Images PMID:861093

  20. [Genesis of auricular fibrillation in the Wolff-Parkinson-White syndrome].

    PubMed

    Gressard, A; Atallah, G; Chatelain, M T; Touboul, P

    1981-11-01

    Atrial fibrillation seems to be more common in the absence of associated cardiac disease in the Wolff-Parkinson-White syndrome (WPW) than in subjects of the same age without this condition. The aim of this study was to analyse the electrophysiological mechanism of AF and to establish its relationship to the accessory pathway. The series comprises 14 out of 51 patients with WPW undergoing classical endocavitary investigation associating the recording of cardiac potentials from the His bundle, right atrium (RA), left atrium (LA) via the coronary sinus and atrial and ventricular stimulation techniques. Three mechanisms of inducing AF were analysed : - AF triggered by RA stimulation : either by a premature extra stimulus or overdrive atrial pacing. In all cases, the accessory pathway was right sides. - AF triggered by overdrive ventricular pacing : three cases were left sided accessory pathways in which atrial desynchronisation was localised in the LA. - Conversion of reciprocating tachycardia to AF (9 cases). In 2 cases, this was preceded by a progressive acceleration of the heart rate. Of 3 left sided accessory pathways, the atrial desynchronisation was located in the LA in 2 cases. The factors which facilitate AF in THE WPW syndrome are discussed : increased atrial vulnerability, the role of the rapid return of ventricular excitation to the atria through the accessory pathway. Our observations suggest that the accessory pathway plays a role in the genesis of AF in the WPW syndrome.

  1. [The double ventricular response phenomenon in 2 cases of Wolff-Parkinson-White syndrome].

    PubMed

    Guize, L; Meilhac, B; Cabanis, C; Di Mattéo, J; Maurice, P

    1978-02-01

    The authors report two cases of "true" consecutive double ventricular response caused by a single premature atrial stimulation; both were young men with Wolff-Parkinson-White syndrome. In both cases, the presence of a bundle of Kent was confirmed. The phenomenon of double ventricular response arising successively from the bundle of Kent and node-His pathway is rare, being mentioned in only two cases in the literature. It is only found when there is the combination of a good bundle of Kent, fair forward conduction, and a relative ventricle-His retrograde block. Amongst the other mechanisms for double ventricular repsonse, re-entry from branch to branch presents the most difficult differential diagnosis. From our observations, the forward characteristics of the spread through the bundle of His which always procedes the bundle of His which always precedes the second ventricular complex have been confirmed, especially in view of the freat variation in the position of this potential which can easily be explained by variations in intra-nodal conduction. In one of these cases, the atriogram, taken after the second ventriculogram, was provided by retrograde activity in the bundle of Kent.

  2. [Prognosis of Wolff-Parkinson-White syndrome in infants. Apropos of 31 cases].

    PubMed

    Becquart, J; Vaksmann, G; Becquart, V; Dupuis, C

    1988-05-01

    The fate of 31 children (18 boys, 13 girls) whose Wolff-Parkinson-White syndrome (WPW) had been diagnosed before they were 2 years' old (mean 3.4 months) was investigated. The circumstances in which WPW was discovered were: evaluation of a heart disease in 9 cases, attack of orthodromic tachycardia in 16 cases (including one with cardiopathy), and routine electrocardiography in 6 cases. Type A WPW was the most frequent, being found in 20 patients of whom only 3 had a heart disease; type B WPW was present in 11 patients, and 7 of these had a heart disease. Mean follow-up was 5.9 years; 3 children died of other causes than WPW. In patients followed up for more than one year WPW disappeared in 65 p. 100 of the cases (11/17) in the absence of cardiopathy, and in only 14 p. 100 of the cases (1/7) in the presence of cardiopathy. In children who had suffered attacks of tachycardia WPW disappeared in 64 p. 100 of the cases (9/14). When WPW disappeared it was before the age of 1 year in 8 out of 12 cases. Only one child whose WPW had disappeared had further attacks of tachycardia (11 p. 100), while 3 children whose WPW persisted had short and widely spaced attacks (60 p. 100). This study confirms the high rate of spontaneous disappearance of WPW and the excellent prognosis of this syndrome in the absence of heart disease.

  3. Native vs photoinduced chemiluminescence in dimethoate determination.

    PubMed

    Catalá-Icardo, M; López-Paz, J L; Choves-Barón, C; Peña-Bádena, A

    2012-01-13

    The determination of dimethoate using either its native chemiluminescent (CL) properties or its photoinduced chemiluminescence obtained by irradiation with a 15 W low-pressure mercury lamp was studied. Thereby, two flow injection systems (FIA) with and without irradiation were exhaustively optimized and their analytical characteristics studied. Better sensitivity and selectivity was found in absence of irradiation, due to the enhancing effect of hexadecylpyridinium chloride (HPC), which acted as a sensitizer. In the developed FIA-CL system, the alkaline hydrolysis of dimethoate with NaOH was performed on-line in presence of HPC. The oxidation of the product of hydrolysis with Ce(IV) in hydrochloric medium induced chemiluminescence. The method provided a limit of detection of only 0.05 ng mL(-1) without any pre-treatment. However, the combination with solid phase extraction allowed the removal of some potential interferents as well as the preconcentration of the pesticide. Finally, the developed method was successfully applied to natural waters with recoveries between 95 and 108%.

  4. Photoinduced formation of thiols in human hair.

    PubMed

    Fedorkova, M V; Brandt, N N; Chikishev, A Yu; Smolina, N V; Balabushevich, N G; Gusev, S A; Lipatova, V A; Botchey, V M; Dobretsov, G E; Mikhalchik, E V

    2016-11-01

    Raman, scanning electron, and optical microscopy of hair and spectrophotometry of soluble hair proteins are used to study the effect of UV-vis radiation on white hair. The samples of a healthy subject are irradiated using a mercury lamp and compared with non-irradiated (control) hair. The cuticle damage with partial exfoliation is revealed with the aid of SEM and optical microscopy of semifine sections. Gel filtration chromatography shows that the molecular weight of soluble proteins ranges from 5 to 7kDa. Absorption spectroscopy proves an increase in amount of thiols in a heavier fraction of the soluble proteins of irradiated samples under study. Raman data indicate a decrease in the amount of SS and CS bonds in cystines and an increase in the amount of SH bonds due to irradiation. Such changes are more pronounced in peripheral regions of hair. Conformational changes of hair keratins presumably related to the cleavage of disulfide bonds, follow from variations in amide I and low-frequency Raman bands. An increase in the content of thiols in proteins revealed by both photometric data on soluble proteins and Raman microspectroscopy of hair cuts can be used to develop a protocol of the analysis of photoinduced hair modification.

  5. Photoinduced chemiluminescence determination of carbamate pesticides.

    PubMed

    Catalá-Icardo, M; Meseguer-Lloret, S; Torres-Cartas, S

    2016-05-11

    A liquid chromatography method with post-column photoinduced chemiluminescence (PICL) detection is proposed for the simultaneous determination of eight carbamate pesticides, namely aldicarb, butocarboxim, ethiofencarb, methomyl, methiocarb, thiodicarb, thiofanox and thiophanate-methyl. After chromatographic separation, quinine (sensitizer) was incorporated and the flow passed through an UV lamp (67 s of irradiation time) to obtain the photoproducts, which reacted with acidic Ce(iv) and provided a CL emission. The PICL method showed great selectivity for carbamate pesticides containing sulphur in their chemical structure. A solid-phase extraction process increased sensitivity (LODs ranging from 0.06 to 0.27 ng mL(-1)) and allowed the carbamate pesticides in surface and ground water samples to be determined, with recoveries in the range 87-110% (except for thiophanate-methyl, whose recoveries were between 60 and 75%). The intra- and inter-day precision was evaluated, with RSD ranging from 1.1 to 7.5% and from 2.6 to 12.3%, respectively. A discussion about the PICL mechanism is also included.

  6. Photoinduced electron transfer in ordered polymers

    SciTech Connect

    Jones, G. II.

    1991-12-01

    Long range photoinduced electron transfer between electron donor and acceptor groups is of considerable current interest in terms of strategies for artificial photosynthesis and studies regarding the redox properties of proteins. As part of an extensive study of long range electron transfer involving biopolymers, we have carried out this year investigations of the assembly of electron transfer agents in a system of model short peptides. Also studied is a polyelectrolyte that can adopt a helical conformation when electrostatically complexed with organic dye counter-ions. The principal interest in these systems has to do with the well ordered secondary structures adopted by peptide polymers, and the capabilities for synthetic modification of peptide side chains and end groups with chromophores or electroactive substituents. The present report gives a brief account of the following elements of work related to photochemical electron transfer themes: (1) the synthesis and photochemical characterization of chromophore-bound peptides and amino acid model compounds based on the amino acids, tryptophan and the spacer residue, alanine (Ala); (2) the study of binding of the cationic organic dye to a peptide electrolyte, for which cooperative dye loading and helix formation is important; and (3) completion of the synthesis of a new series of acridinium chromophores that have rod-like'' arrangements of inked aryl rings for assembly of electron donor-acceptor systems that will exhibit especially long lived charge separation.

  7. Inactivation of tyrosinase photoinduced by pterin

    SciTech Connect

    Laura Dantola, M.; Gojanovich, Aldana D.; Thomas, Andres H.

    2012-08-03

    Highlights: Black-Right-Pointing-Pointer Under UV-A radiation, tirosinase is photoinactivated by pterin. Black-Right-Pointing-Pointer The mechanism involves an electron transfer-initiated process. Black-Right-Pointing-Pointer The photochemical process affects both activities of tyrosinase. -- Abstract: Tyrosinase catalyzes in mammals the first and rate-limiting step in the biosynthesis of the melanin, the main pigment of the skin. Pterins, heterocyclic compounds able to photoinduce oxidation of DNA and its components, accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder in which the protection against UV radiation fails due to the lack of melanin. Aqueous solutions of tyrosinase were exposed to UV-A irradiation (350 nm) in the presence of pterin, the parent compound of oxidized pterins, under different experimental conditions. The enzyme activity in the irradiated solutions was determined by spectrophotometry and HPLC. In this work, we present data that demonstrate unequivocally that the enzyme is photoinactivated by pterin. The mechanism of the photosensitized process involves an electron transfer from tyrosinase to the triplet excited state of pterin, formed after UV-A excitation of pterin. The biological implications of the results are discussed.

  8. The cytogenetics of mammalian autosomal rearrangements

    SciTech Connect

    Daniel, A. )

    1988-01-01

    This book is covered under the following topics: Ascertainment and risks of recombinant progeny; Infertility, gametic selection, and fetal loss; origin of chromosome rearrangements; and Some implications of chromosome breakpoints.

  9. Glycolytic regulation of cell rearrangement in angiogenesis

    PubMed Central

    Cruys, Bert; Wong, Brian W.; Kuchnio, Anna; Verdegem, Dries; Cantelmo, Anna Rita; Conradi, Lena-Christin; Vandekeere, Saar; Bouché, Ann; Cornelissen, Ivo; Vinckier, Stefan; Merks, Roeland M. H.; Dejana, Elisabetta; Gerhardt, Holger; Dewerchin, Mieke; Bentley, Katie; Carmeliet, Peter

    2016-01-01

    During vessel sprouting, endothelial cells (ECs) dynamically rearrange positions in the sprout to compete for the tip position. We recently identified a key role for the glycolytic activator PFKFB3 in vessel sprouting by regulating cytoskeleton remodelling, migration and tip cell competitiveness. It is, however, unknown how glycolysis regulates EC rearrangement during vessel sprouting. Here we report that computational simulations, validated by experimentation, predict that glycolytic production of ATP drives EC rearrangement by promoting filopodia formation and reducing intercellular adhesion. Notably, the simulations correctly predicted that blocking PFKFB3 normalizes the disturbed EC rearrangement in high VEGF conditions, as occurs during pathological angiogenesis. This interdisciplinary study integrates EC metabolism in vessel sprouting, yielding mechanistic insight in the control of vessel sprouting by glycolysis, and suggesting anti-glycolytic therapy for vessel normalization in cancer and non-malignant diseases. PMID:27436424

  10. "Effects of networking on career success: A longitudinal study": Correction to Wolff and Moser (2009).

    PubMed

    2017-02-01

    Reports an error in "Effects of networking on career success: A longitudinal study" by Hans-Georg Wolff and Klaus Moser (Journal of Applied Psychology, 2009[Jan], Vol 94[1], 196-206). In the article, results from a confirmatory factor analysis on subjective career success in the Measures section contained an error in the reported Chi-square (i.e., χ² (5, N = 257) = 9.17). This error does not alter any conclusions or substantive statements in the original article. The correct fit indices are " χ²(5, N = 257) 9.67, p = .08, RMSEA = 0.059, CFI = 1.00." (The following abstract of the original article appeared in record 2009-00697-007.) Previous research has reported effects of networking, defined as building, maintaining, and using relationships, on career success. However, empirical studies have relied exclusively on concurrent or retrospective designs that rest upon strong assumptions about the causal direction of this relation and depict a static snapshot of the relation at a given point in time. This study provides a dynamic perspective on the effects of networking on career success and reports results of a longitudinal study. Networking was assessed with 6 subscales that resulted from combining measures of the facets of (a) internal versus external networking and (b) building versus maintaining versus using contacts. Objective (salary) and subjective (career satisfaction) measures of career success were obtained for 3 consecutive years. Multilevel analyses showed that networking is related to concurrent salary and that it is related to the growth rate of salary over time. Networking is also related to concurrent career satisfaction. As satisfaction remained stable over time, no effects of networking on the growth of career satisfaction were found. (PsycINFO Database Record

  11. A 2003 update of bone physiology and Wolff's Law for clinicians.

    PubMed

    Frost, Harold M

    2004-02-01

    By 1892, Julius Wolff and others realized that mechanical loads can affect bone architecture in living beings, but the mechanisms responsible for this effect were unknown, and it had no known clinical applications. In 2003 we know how this effect occurs and some of its applications. Our load-bearing bones (LBBs) include tibias, femurs, humeri, vertebrae, radii, mandibles, maxillae, wrists, hips, etc (so LBBs are not limited to weight-bearing ones). The strength of such bones and their trabeculae would represent their most important physiologic feature but in the special sense of relative to the size of the typical peak voluntary loads on them. The biologic "machinery" that determines whole-bone strength forms a tissue-level negative feedback system called the mechanostat. Two thresholds make a bone's strains determine its strength by switching on and off the biologic mechanisms that increase or decrease its strength. Equally, two thermostats can determine a room's temperature by switching on and off the room's heating and cooling systems. General features show that the largest voluntary loads on LBBs determine most of their strength after birth. These loads come from muscle forces so muscle strength strongly influences the strength of our LBBs. This process affects, in part, the healing of fractures, bone grafts, osteotomies, and arthrodeses; the bone's ability to endure load-bearing joint and dental endoprostheses; why healthy bones are stronger than the minimum needed to keep voluntary loads from breaking them suddenly or from fatigue; some general functions and disorders of bone modeling and basic multicellular unit-based bone remodeling; some limitations of in vitro data and of pharmaceutical actions; and the fact that many bone-active humoral and local agents have permissive roles in a bone's adaptations and healing, instead of forcing them to occur.

  12. [Should the Isuprel test be performed systematically in Wolff-Parkinson-White syndrome?].

    PubMed

    Brembilla-Perrot, B; Terrier de la Chaise, A; Marçon, F; Cherrier, F; Pernot, C

    1988-10-01

    The isoprenaline (Is) test was designed by Wellens et al. in 1982 to evaluate the effect of catecholamines on the effective refractory period (ERP) of Kent's bundle (K). The purpose of our study was to assess the value of this test in the prognosis of Wolff-Parkinson-White syndrome (WPW), to define its criteria of severity and to determine the usefulness of the test. Out of 33 patients with WPW syndrome, 10 (group I) had a clinical history of severe arrhythmia and 23 (group II) were asymptomatic or had paroxysmal nodal tachycardia. The prognosis of WPW syndrome was evaluated by measuring Kent's bundle ERP under coupled atrial stimulation (S1 S2) and the shortest cycle conducted by K during induced atrial fibrillation (AF) and atrial pacing (AP) both in the basal state (B) and under a 20-30 micrograms Is infusion. (table; see text). Analysis of the results showed constant shortening of ERP in group I and reproduction of the clinical tachycardia in 6 cases. In group II patients isoprenaline unmasked the WPW syndrome in 3 cases and reproduced the clinical tachycardia in 5 cases. The ERP of Kent's bundle evaluated by S1 S2 became smaller or equal to 220 ms in 70 p. 100 of the cases, and this shortening was not specific. The shortest cycle in AF or AP became inferior of equal to 220 ms in only 6 cases, the history being concordant with clinical findings in 4 of them. Altogether, the most reliable and simplest way of evaluating the severity of WPW syndrome is the highest frequency conducted by Kent's bundle in atrial pacing during the Is test which should be performed in all patients in view of its specificity, simplicity and safety.

  13. Photoinduced electro-optics measurements of biosilica transformation to cristobalite

    NASA Astrophysics Data System (ADS)

    Fuchs, Ido; Aluma, Yaniv; Ilan, Micha; Kityk, Iwan; Mastai, Yitzhak

    2015-03-01

    In this paper we studied the photoinduced electro optics effects in the thermal transformation process of biosilica to cristobalite, at a relatively low temperature and ambient pressure. This process was characterized by a variety of standards techniques with emphasis on linear electro optic effect measurements. Overall we demonstrated that photoinduced electro optics measurements are very sensitive to the transformation from amorphous structure of silica in the natural sponge samples to laminar string morphology of cristobalite. With this technique we could probe the change in the samples chirality from achiral bio silica to chiral cristobalite structure. Furthermore it is shown that natural biosilica have photoinduced linear electro optics respond indicating the chiral natural of biosilica.

  14. Photoinduced structural changes to protein kinase A

    NASA Astrophysics Data System (ADS)

    Rozinek, Sarah C.; Thomas, Robert J.; Brancaleon, Lorenzo

    2014-03-01

    The importance of porphyrins in organisms is underscored by the ubiquitous biological and biochemical functions that are mediated by these compounds and by their potential biomedical and biotechnological applications. Protoporphyrin IX (PPIX) is the precursor to heme and has biomedical applications such as its use as a photosensitizer in phototherapy and photodetection of cancer. Among other applications, our group has demonstrated that low-irradiance exposure to laser irradiation of PPIX, Fe-PPIX, or meso-tetrakis (4-sulfonatophenyl) porphyrin (TSPP) non-covalently docked to a protein causes conformational changes in the polypeptide. Such approach can have remarkable consequences in the study of protein structure/function relationship and can be used to prompt non-native protein properties. Therefore we have investigated protein kinase A (PKA), a more relevant protein model towards the photo-treatment of cancer. PKA's enzymatic functions are regulated by the presence of cyclic adenosine monophosphate for intracellular signal transduction involved in, among other things, stimulation of transcription, tumorigenesis in Carney complex and migration of breast carcinoma cells. Since phosphorylation is a necessary step in some cancers and inflammatory diseases, inhibiting the protein kinase, and therefore phosphorylation, may serve to treat these diseases. Changes in absorption, steady-state fluorescence, and fluorescence lifetime indicate: 1) both TSPP and PPIX non-covalently bind to PKA where they maintain photoreactivity; 2) absorptive photoproduct formation occurs only when PKA is bound to TSPP and irradiated; and 3) PKA undergoes secondary structural changes after irradiation with either porphyrin bound. These photoinduced changes could affect the protein's enzymatic and signaling capabilities.

  15. A study of dynamic finite size scaling behavior of the scaling functions—calculation of dynamic critical index of Wolff algorithm

    NASA Astrophysics Data System (ADS)

    Gündüç, Semra; Dilaver, Mehmet; Aydın, Meral; Gündüç, Yiğit

    2005-02-01

    In this work we have studied the dynamic scaling behavior of two scaling functions and we have shown that scaling functions obey the dynamic finite size scaling rules. Dynamic finite size scaling of scaling functions opens possibilities for a wide range of applications. As an application we have calculated the dynamic critical exponent (z) of Wolff's cluster algorithm for 2-, 3- and 4-dimensional Ising models. Configurations with vanishing initial magnetization are chosen in order to avoid complications due to initial magnetization. The observed dynamic finite size scaling behavior during early stages of the Monte Carlo simulation yields z for Wolff's cluster algorithm for 2-, 3- and 4-dimensional Ising models with vanishing values which are consistent with the values obtained from the autocorrelations. Especially, the vanishing dynamic critical exponent we obtained for d=3 implies that the Wolff algorithm is more efficient in eliminating critical slowing down in Monte Carlo simulations than previously reported.

  16. Electrophysiology testing and catheter ablation are helpful when evaluating asymptomatic patients with Wolff-Parkinson-White pattern: the con perspective.

    PubMed

    Skanes, Allan C; Obeyesekere, Manoj; Klein, George J

    2015-09-01

    The association between asymptomatic Wolff-Parkinson-White (WPW) syndrome and sudden cardiac death (SCD) has been well documented. The inherent properties of the accessory pathway determine the risk of SCD in WPW, and catheter ablation essentially eliminates this risk. An approach to WPW syndrome is needed that incorporates the patient's individualized considerations into the decision making. Patients must understand that there is a trade-off of a small immediate risk of an invasive approach for elimination of a small lifetime risk of the natural history of asymptomatic WPW. Clinicians can minimize the invasive risk by only performing ablation for patients with at-risk pathways.

  17. Ventricular fibrillation development following atrial fibrillation after the ingestion of sildenaphil in a patient with Wolff-Parkinson-White syndrome

    PubMed Central

    Inci, Sinan; Izgu, Ibrahim; Aktas, Halil; Dogan, Pinar; Dogan, Ali

    2015-01-01

    Summary Complications in the accessory pathway in Wolff-Parkinson-White (WPW) syndrome could cause different clinical conditions by inducing different arrhythmias. Atrial fibrillation (AF) is one of these arrhythmias and is important as it causes life-threatening arrhythmias. It is known that some drugs, underlying cardiac diseases, and the number of accessory pathways, cause a predisposition to this condition. In the current report, we presented a patient with WPW who was admitted to the emergency department with AF, wide QRS and a rapid ventricular response that progressed to ventricular fibrillation. PMID:26361569

  18. [Obvious or inapparent Wolff-Parkinson-White syndrome associated with duality of nodal conduction. Apropos of 4 cases].

    PubMed

    Motté, G; Belhassen, B; Bodereau, P

    1979-03-01

    In a series of 48 patients undergoing electrophysiological investigation for attacks of reciprocating tachycardia related to concealed or overt Wolff-Parkinson-White syndrome in sinus rhythm, 4 patients were found to have duality of nodal conduction. This association was responsible for several tachycardia circuits: in 2 patients the activation passed constantly retrogradely through the accessory pathway and then either through the slow nodal pathway or the rapid nodal pathway in the anterograde direction. In the other two patients, in addition to classical orthodromic tachycardia, purely intranodal reciprocating rhythms giving rise to sustained tachycardia in one case and to simple echos in the other, were observed.

  19. Spontaneous Transition of Double Tachycardias with Atrial Fusion in a Patient with Wolff-Parkinson-White Syndrome

    PubMed Central

    Kim, Dongmin

    2016-01-01

    Among patients with Wolff-Parkinson-White syndrome, atrioventricular reciprocating tachycardia (AVRT) and atrioventricular nodal reentrant tachycardia (AVNRT) can coexist in a single patient. Direct transition of both tachycardias is rare; however, it can occur after premature atrial or ventricular activity if the cycle lengths of the two tachycardias are similar. Furthermore, persistent atrial activation by an accessory pathway (AP) located outside of the AV node during ongoing AVNRT is also rare. This article describes a case of uncommon atrial activation by an AP during AVNRT and gradual transition of the two supraventricular tachycardias without any preceding atrial or ventricular activity in a patient with preexcitation syndrome. PMID:27482269

  20. Photoinduced charge separation by polymer-bound chromophores

    SciTech Connect

    Rodgers, M.A.J.

    1991-09-01

    This project has examined the photodynamic behavior of water-soluble polymers that have covalently linked hydrophobic chromophores spaced along the chains. These polymeric systems have been examined for photoinduced charge separation with electron-accepting ions having different total charge. Focus has been on the excited singlet (S{sub 1}) state formed by laser flash absorption. The effects of pH and ionic strength -- factors that govern the conformational nature of the polymer in solution -- have been studied. A second major effort has been to study photoinduced redox processes involving excited states of water-soluble variants of anthracene and acridine. 27 refs., 16 figs., 2 tabs.

  1. Photo-induced chaos in the Briggs-Rauscher reaction

    NASA Astrophysics Data System (ADS)

    Okazaki, Noriaki; Hanazaki, Ichiro

    1998-07-01

    Discovery of the photo-induced chaos in the Briggs-Rauscher system is reported. The chaotic oscillations were observed between the large- and the small-amplitude simple oscillatory states existent in low and high light intensity regions, respectively. Period-doubling sequence from the large-amplitude oscillations to the chaos was observed. Deterministic nature of the chaos was confirmed by the next-amplitude return map. The stretching and folding mechanism of the trajectories was revealed through the three-dimensional attractor reconstructed via the singular value decomposition method. The chemical origin of the photoinduced chaos is discussed based on the photoautocatalysis of HIO2.

  2. Quantitative analysis of sideband coupling in photoinduced force microscopy

    NASA Astrophysics Data System (ADS)

    Jahng, Junghoon; Kim, Bongsu; Lee, Eun Seong; Potma, Eric Olaf

    2016-11-01

    We present a theoretical and experimental analysis of the cantilever motions detected in photoinduced force microscopy (PiFM) using the sideband coupling detection scheme. In sideband coupling, the cantilever dynamics are probed at a combination frequency of a fundamental mechanical eigenmode and the modulation frequency of the laser beam. Using this detection mode, we develop a method for reconstructing the modulated photoinduced force gradient from experimental parameters in a quantitative manner. We show evidence, both theoretically and experimentally, that the sideband coupling detection mode provides PiFM images with superior contrast compared to images obtained when detecting the cantilever motions directly at the laser modulation frequency.

  3. The nature and role of bridged carbonyl intermediates in theultrafast photo-induced rearrangement of Ru3(CO)12.

    SciTech Connect

    Glascoe, Elizabeth A.; Kling, Matthias F.; Shanoski, Jennifer E.; Harris, Charles B.

    2005-09-18

    The photochemistry of the trimetal cluster,Ru(3)(CO)12, was investigated on the ultrafast timescale using UV-vis pump, infrared probe spectroscopy in order to study the transient intermediates formed upon photoexcitation.

  4. Cortical microtubule rearrangements and cell wall patterning

    PubMed Central

    Oda, Yoshihisa

    2015-01-01

    Plant cortical microtubules, which form a highly ordered array beneath the plasma membrane, play essential roles in determining cell shape and function by directing the arrangement of cellulosic and non-cellulosic compounds on the cell surface. Interphase transverse arrays of cortical microtubules self-organize through their dynamic instability and inter-microtubule interactions, and by branch-form microtubule nucleation and severing. Recent studies revealed that distinct spatial signals including ROP GTPase, cellular geometry, and mechanical stress regulate the behavior of cortical microtubules at the subcellular and supercellular levels, giving rise to dramatic rearrangements in the cortical microtubule array in response to internal and external cues. Increasing evidence indicates that negative regulators of microtubules also contribute to the rearrangement of the cortical microtubule array. In this review, I summarize recent insights into how the rearrangement of the cortical microtubule array leads to proper, flexible cell wall patterning. PMID:25904930

  5. New anticancer antibiotic acts through diradical rearrangement

    SciTech Connect

    Stinson, S. )

    1990-05-28

    This paper reports that chemists have found and characterized an anticancer antibiotic, dynemicin A, that may be the fouth of a series of antibiotics that act by metabolic rearrangement to a diradical. If true, diradical precursors may represent an antibiotic strategy that evolved widely in nature. And, there may be many more anticancer antibiotics awaiting discovery. Also, the unique internal trigger that seems to set off the dynemicin rearrangement gives chemists a new understanding of how these compounds work. If, indeed, the anthraquinone nucleus in dynemicin A binds by intercalation between strands of DNA as is now thought, chemists will learn more about how to deliver drugs to specific sites.

  6. Facile Oxidative Rearrangements Using Hypervalent Iodine Reagents

    PubMed Central

    Singh, Fateh V; Rehbein, Julia; Wirth, Thomas

    2012-01-01

    Aromatic substituents migrate in a novel oxidative cyclization mediated by iodine(III) reagents. 4-Arylbut-3-enoic acids are cyclized and rearranged to 4-arylfuran-2(5H)-ones by hypervalent iodine compounds in good to excellent yields under mild reaction conditions. Other ring sizes are also accessible. The mechanism of the reaction is described in detail, and calculations highlight the cationic nature of the intermediates in the rearrangement. The fast access to heavily substituted furanones is used for the synthesis of biologically active derivatives. PMID:24551514

  7. [Prevalence and electrocardiographic forms of the Wolff-Parkinson-White syndrome].

    PubMed

    Soria, R; Guize, L; Fernandez, F; Chaouat, J C; Chrétien, J M

    1982-12-01

    In a routine electrocardiographic study of 133929 subjects aged from 20 to 73, 136 cases of the Wolff-Parkinson-White syndrome were detected, 6 with intermittent pre-excitation. In this study, the prevelance of WPW was about 1 in a 1000, the highest incidence being in the 20-40 year age group with an equal sex ratio. The ECG analysis of the 136 cases consisted in determining the orientation of the delta wave in the precordial leads to establish the right or left ventricular origin of the pre-excitation, calculating the direction of the delta wave vector in the frontal plane to find out the anterior, lateral or posterior origin of the pre-excitation and analyse the position of the QRS axis to assess the appearances of the latest ventricular activity. The 136 ECGs were then classified according to electrophysiological criteria and the results of mapping: 1. Left ventricular pre-excitation; 74 cases characterised by a dominant delta wave in the right precordial leads. These cases were subdivided into: - 30 cases with posterior paraseptal pre-excitation, axis of the delta wave deviated superiorly and to the left, between -30 degrees and -60 degrees; - 20 cases of lateral pre-excitation with the vector of the delta wave deviated inferiorly and to the right between +100 degrees and +120 degrees; - 24 cases of anterior paraseptal pre-excitation with high amplitude delta and QRS deflections in all precordial leads and a delta wave axis between +50 degrees and +80 degrees. 2. Right ventricular pre-excitation; 62 cases characterised by a negative or isoelectric delta wave in the right precordial leads, including: - 14 posterior paraseptal pre-excitation with significant delta wave axis deviation between -30 degrees and -60 degrees; - 33 lateral pre-excitation with the delta and QRS axis pointing directly to the left at about 0 degrees; - 15 cases of anterior paraseptal pre-excitation with the delta wave axis between +50 degrees and +80 degrees. The cases with terminal forces

  8. Measurements of Photo-induced Changes in Conjugated Polymers

    DOE R&D Accomplishments Database

    Seager, C. H.; Sinclair, M. B.; Mc Branch, D.; Heeger, A. J.; Baker, G. L.

    1991-01-01

    We have used the highly sensitive technique of Photothermal Deflection Spectroscopy (PDS) to measure changes in the infrared absorption spectra of MEHPPV, P3HT and Polydiacetylene-4BCMU induced by pumping these polymers with light above the {pi} - {pi}* transition energy. In contrast to previous chopped light transmission measurements of these effects, the PDS technique can directly measure the buildup or decay of the absorption coefficient, {alpha}, on the time scale of second to days. In the case of MEHPPV we observe that the time scale of seconds to days. In the case of MEHPPV we observe that above-gap light causes the appearance of a broad infrared peak in {alpha}, which continues to grow-in hours after the pump light is first applied. For this polymer the general shape of the absorption spectra in the unpumped state mimics the photo-induced changes, suggesting that remnant photo-induced states determine the maximum transparency observed under normal experimental conditions. For P3HT and to a lesser extent, MEHPPV, we also observe irreversible photo-induced absorption components which we tentatively identify with photo-induced oxidation of the polymer matrix.

  9. Genomic rearrangements at rrn operons in Salmonella.

    PubMed

    Helm, R Allen; Lee, Alison G; Christman, Harry D; Maloy, Stanley

    2003-11-01

    Most Salmonella serovars are general pathogens that infect a variety of hosts. These "generalist" serovars cause disease in many animals from reptiles to mammals. In contrast, a few serovars cause disease only in a specific host. Host-specific serovars can cause a systemic, often fatal disease in one species yet remain avirulent in other species. Host-specific Salmonella frequently have large genomic rearrangements due to recombination at the ribosomal RNA (rrn) operons while the generalists consistently have a conserved chromosomal arrangement. To determine whether this is the result of an intrinsic difference in recombination frequency or a consequence of lifestyle difference between generalist and host-specific Salmonella, we determined the frequency of rearrangements in vitro. Using lacZ genes as portable regions of homology for inversion analysis, we found that both generalist and host-specific serovars of Salmonella have similar tolerances to chromosomal rearrangements in vitro. Using PCR and genetic selection, we found that generalist and host-specific serovars also undergo rearrangements at rrn operons at similar frequencies in vitro. These observations indicate that the observed difference in genomic stability between generalist and host-specific serovars is a consequence of their distinct lifestyles, not intrinsic differences in recombination frequencies.

  10. Facility rearrangement scoping study: Draft letter report

    SciTech Connect

    Not Available

    1987-04-17

    We assessed the feasibility of designing the salt repository layouts so that shafts, surface structures and facilities would be totally within the north-east (NE) and center-east (CE) (one square mile) sections of the 9 square mile Deaf Smith site. With the latest version of the SCP-Conceptual Design as the basis, rearrangement analyses were conducted for the surface and subsurface layouts. For the rearranged layouts that were workable, impact assessments, relative to the SCP-Conceptual Design, were performed. This study concluded that, on a qualitative basis, the salt repository surface facilities can be relocated to within the north-east and center-east sections of the site. A suitable subsurface layout can be designed to accommodate this rearrangement. The resultant surface rearrangement is depicted. The two study sections (NE and CE) are emphasized on this figure. For reference, the location of the surface facilities in the SCP-Conceptual Design is also shown. 11 refs., 1 tab.

  11. Light chain replacement: a new model for antibody gene rearrangement

    PubMed Central

    1995-01-01

    A functional B cell antigen receptor is thought to regulate antibody gene rearrangement either by stopping further rearrangement (exclusion) or by promoting additional rearrangement (editing). We have developed a new model to study the regulation of antibody gene rearrangement. In this model, we used gene targeting to replace the J kappa region with a functional V kappa-J kappa light chain gene. Two different strains of mice were created; one, V kappa 4R, has a V kappa 4-J kappa 4 rearrangement followed by a downstream J kappa 5 segment, while the other, V kappa 8R, has a V kappa 8-J kappa 5 light chain. Here, we analyze the influence of these functional light chains on light chain rearrangement. We show that some V kappa 4R and V kappa 8R B cells only have the V kappa R light chain rearrangement, whereas others undergo additional rearrangements. Additional rearrangement can occur not only at the other kappa allele or isotype (lambda), but also at the targeted locus in both V kappa 4R and V kappa 8R. Rearrangement to the downstream J kappa 5 segment is observed in V kappa 4R, as is deletion of the targeted locus in both V kappa 4R and V kappa 8R. The V kappa R models illustrate that a productively rearranged light chain can either terminate further rearrangement or allow further rearrangement. We attribute the latter to editing of autoantibodies and to corrections of dysfunctional receptors. PMID:7629511

  12. Deep cytoplasmic rearrangements in ventralized Xenopus embryos

    NASA Technical Reports Server (NTRS)

    Brown, E. E.; Denegre, J. M.; Danilchik, M. V.

    1993-01-01

    Following fertilization in Xenopus, dramatic rearrangements of the egg cytoplasm relocalize maternally synthesized egg components. During the first cell cycle the vegetal yolk mass rotates relative to the egg surface, toward the sperm entry point (SEP) (J. P. Vincent, G. F. Oster, and J. C. Gerhart, 1986, Dev. Biol. 113, 484-500), while concomitant deep cytoplasmic rearrangements occur in the animal hemisphere (M. V. Danilchik and J. M. Denegre, 1991, Development 111, 845-856). In this paper we examine the role of vegetal yolk mass rotation in producing the animal cytoplasmic rearrangements. We inhibited rotation by uv-irradiating embryos during the first cell cycle, a treatment that yields an extremely ventralized phenotype. Both uv-irradiated embryos and unirradiated control embryos show cytoplasmic rearrangements in the animal hemisphere during the first cell cycle. Cytoplasmic rearrangements on the SEP side of the embryo associated with the path of the sperm pronucleus, plus a swirl on the anti-SEP (dorsal) side, are seen, whether or not yolk mass rotation has occurred. This result suggests a role for the expanding sperm aster in directing animal hemisphere cytoplasmic movements. In unirradiated control embryos the anti-SEP (dorsal) swirl is larger than that in uv-irradiated embryos and often extends into the vegetal hemisphere, consistent with the animal cytoplasm having been pulled dorsally and vegetally by the sliding vegetal yolk mass. Thus the yolk mass rotation may normally enhance the dorsalward cytoplasmic movement, begun by the sperm aster, enough to induce normal axis formation. We extended our observations of unirradiated control and uv-irradiated embryos through early cleavages. The vegetal extent of the anti-SEP (dorsal) swirl pattern seen in control embryos persists through the early cleavage period, such that labeled animal cytoplasm extends deep into dorsal third-tier blastomeres at the 32-cell stage. Significantly, in uv-irradiated embryos

  13. Dynamics of genome rearrangement in bacterial populations.

    PubMed

    Darling, Aaron E; Miklós, István; Ragan, Mark A

    2008-07-18

    Genome structure variation has profound impacts on phenotype in organisms ranging from microbes to humans, yet little is known about how natural selection acts on genome arrangement. Pathogenic bacteria such as Yersinia pestis, which causes bubonic and pneumonic plague, often exhibit a high degree of genomic rearrangement. The recent availability of several Yersinia genomes offers an unprecedented opportunity to study the evolution of genome structure and arrangement. We introduce a set of statistical methods to study patterns of rearrangement in circular chromosomes and apply them to the Yersinia. We constructed a multiple alignment of eight Yersinia genomes using Mauve software to identify 78 conserved segments that are internally free from genome rearrangement. Based on the alignment, we applied Bayesian statistical methods to infer the phylogenetic inversion history of Yersinia. The sampling of genome arrangement reconstructions contains seven parsimonious tree topologies, each having different histories of 79 inversions. Topologies with a greater number of inversions also exist, but were sampled less frequently. The inversion phylogenies agree with results suggested by SNP patterns. We then analyzed reconstructed inversion histories to identify patterns of rearrangement. We confirm an over-representation of "symmetric inversions"-inversions with endpoints that are equally distant from the origin of chromosomal replication. Ancestral genome arrangements demonstrate moderate preference for replichore balance in Yersinia. We found that all inversions are shorter than expected under a neutral model, whereas inversions acting within a single replichore are much shorter than expected. We also found evidence for a canonical configuration of the origin and terminus of replication. Finally, breakpoint reuse analysis reveals that inversions with endpoints proximal to the origin of DNA replication are nearly three times more frequent. Our findings represent the first

  14. Photo-orientation of azobenzene-containing liquid-crystalline materials by means of domain structure rearrangement.

    PubMed

    Bogdanov, Alexey V; Vorobiev, Andrey Kh

    2013-11-07

    A novel mechanism of photo-orientation of azobenzene-containing liquid-crystalline materials is proposed. This mechanism is based on the notion of photochemically induced domain rearrangement driven by destabilization of liquid-crystalline phase in light absorbing domains due to photochemical formation of non-mesogenic cis-azobenzene moieties. The experimental evidence of photoinduced movement of a domain boundary is presented, and the velocity of this movement is measured. A mathematical model for photo-orientation of a polydomain azobenzene-containing material is formulated. The values of model parameters for a liquid-crystalline azopolymer have been measured in separate experiments. Theoretical predictions demonstrate quantitative agreement with the experimental observations.

  15. Afrobatrachian mitochondrial genomes: genome reorganization, gene rearrangement mechanisms, and evolutionary trends of duplicated and rearranged genes

    PubMed Central

    2013-01-01

    Background Mitochondrial genomic (mitogenomic) reorganizations are rarely found in closely-related animals, yet drastic reorganizations have been found in the Ranoides frogs. The phylogenetic relationships of the three major ranoid taxa (Natatanura, Microhylidae, and Afrobatrachia) have been problematic, and mitogenomic information for afrobatrachians has not been available. Several molecular models for mitochondrial (mt) gene rearrangements have been proposed, but observational evidence has been insufficient to evaluate them. Furthermore, evolutionary trends in rearranged mt genes have not been well understood. To gain molecular and phylogenetic insights into these issues, we analyzed the mt genomes of four afrobatrachian species (Breviceps adspersus, Hemisus marmoratus, Hyperolius marmoratus, and Trichobatrachus robustus) and performed molecular phylogenetic analyses. Furthermore we searched for two evolutionary patterns expected in the rearranged mt genes of ranoids. Results Extensively reorganized mt genomes having many duplicated and rearranged genes were found in three of the four afrobatrachians analyzed. In fact, Breviceps has the largest known mt genome among vertebrates. Although the kinds of duplicated and rearranged genes differed among these species, a remarkable gene rearrangement pattern of non-tandemly copied genes situated within tandemly-copied regions was commonly found. Furthermore, the existence of concerted evolution was observed between non-neighboring copies of triplicated 12S and 16S ribosomal RNA regions. Conclusions Phylogenetic analyses based on mitogenomic data support a close relationship between Afrobatrachia and Microhylidae, with their estimated divergence 100 million years ago consistent with present-day endemism of afrobatrachians on the African continent. The afrobatrachian mt data supported the first tandem and second non-tandem duplication model for mt gene rearrangements and the recombination-based model for concerted

  16. Photoinduced "stick-slip" on superhydrophilic semiconductor surfaces.

    PubMed

    Denison, Kieth R; Boxall, Colin

    2007-04-10

    Transparent mesoporous TiO2 (M-TiO2) thin films were prepared on quartz via a reverse micelle, sol-gel, spin-coating technique. Films were characterized by atomic force microscopy (AFM) and Raman and UV-vis spectroscopies and were found to be mostly anatase with low surface roughness (Rt approximately 5 nm). The time dependence of film photoinduced superhydrophilicity (PISH) was measured by observation of the spreading of a sessile water drop using a new, continuous measurement technique wherein the drop was first applied to the semiconductor surface and then was filmed while it and the underlying substrate were illuminated by 315 nm ultraband gap light. Results obtained at 100% relative humidity (RH) at 293 K showed that drops on M-TiO2 surfaces exhibited a photoinduced "stick-slip" behavior, the first time such an effect has been observed. The thermodynamic driving force for this photoinduced stick-slip was the departure of the system from capillary equilibrium as, with increasing illumination time, the concentration of surface Ti-OH groups increased and the equilibrium contact angle of the drop, theta0, decreased. A simple theoretical description of photoinduced stick-slip is derived and is used to calculate a value of the potential energy barrier associated with surface inhomogeneities that oppose onset of movement of the triple line, U = 6.63 x 10(-6) J m(-1). This is the first time that U has been quantified for a surface with photoinduced superhydrophilicity. Triple line retreat measurements on an evaporating drop on M-TiO2 in the dark, RH = 60%, T = 293 K, gave a value of U = 9.4 x 10(-6) J m(-1), indicating that U decreases upon UV illumination and that U in the light is primarily associated with inhomogeneities that are unaffected by an increase in the surface Ti-OH population, such as the physical roughness of the surface. In the dark evaporation experiment, the drop was found to retreat with an areal velocity of 1.48 x 10(-8) m2 s(-1). However, under UV

  17. Wolff-Parkinson-White syndrome type B and left bundle-branch block: electrophysiologic and radionuclide study

    SciTech Connect

    Rakovec, P.; Kranjec, I.; Fettich, J.J.; Jakopin, J.; Fidler, V.; Turk, J.

    1985-01-01

    Coinciding left bundle-branch block and Wolff-Parkinson-White syndrome type B, a very rare electrocardiographic occurrence, was found in a patient with dilated cardiomyopathy. Electrophysiologic study revealed eccentric retrograde atrial activation during ventricular pacing, suggesting right-sided accessory pathway. At programmed atrial pacing, effective refractory period of the accessory pathway was 310 ms; at shorter pacing coupling intervals, normal atrioventricular conduction with left bundle-branch block was seen. Left bundle-branch block was seen also with His bundle pacing. Radionuclide phase imaging demonstrated right ventricular phase advance and left ventricular phase delay; both right and left ventricular phase images revealed broad phase distribution histograms. Combined electrophysiologic and radionuclide investigations are useful to disclose complex conduction abnormalities and their mechanical correlates.

  18. The time of a photoinduced spin-Peierls phase transition

    SciTech Connect

    Semenov, A. L.

    2015-02-15

    The time τ of the spin-Peierls phase transition is analyzed theoretically as a function of the duration τ{sub p} of the exciting light pulse and the average number x{sub 0} of absorbed photons per magnetic ion after the transmission of the pulse. It is shown that the phase transition occurs at x{sub 0} > x{sub c}. The critical value x{sub c} is determined as a function of the duration τ{sub p} of the light pulse. A photoinduced variation in the optical reflection coefficient R is calculated as a function of time t. The results of calculation are compared with experimental data on ultrafast photoinduced melting of the low-temperature spin-Peierls phase into potassium tetracyanoquinodimethan (K-TCNQ)

  19. Heterodyne technique in photoinduced force microscopy with photothermal effect

    NASA Astrophysics Data System (ADS)

    Yamanishi, J.; Naitoh, Y.; Li, Y. J.; Sugawara, Y.

    2017-03-01

    The heterodyne technique is used to detect short-range forces. Using the heterodyne technique, we demonstrate photoinduced force microscopy (PiFM) imaging and z-spectroscopy without the artifact of photothermal vibration. The rejection ratio was at least 99.975% under a high-scattering condition. In addition, the heterodyne technique employs the optimal amplitude at the first resonance frequency of the cantilever to detect the photoinduced force sensitively. According to our calculation, the optimal ratio of the amplitude to the distance between the dipole of the tip and that of the sample is 0.4448. The heterodyne technique can be employed to perform PiFM without the artifact by using the optimal amplitude.

  20. Photo-induced electron-transfer reactions in heterogeneous media

    NASA Astrophysics Data System (ADS)

    Yang, J. M.

    1981-11-01

    The conversion of solar energy into chemical energy was pursued by two approaches. One is the photo-induced electron transfer reactions in heterogeneous media, and the other is the photo-decomposition of water with liquid-junction solar cells. Photo-induced electron-transfer reactions in heterogeneous media with colloidal silica or poly-acrylate were studied by flash photolysis. In an effort to illustrate that small band-gap semiconductors can be protected from photo-corrosion through surface modification, the surface of polycrystalline ZnO was chemically coated with zinc phthalocyanine and the electron-transfer process across the coated ZnO-electrolyte interface was studied by photo-electrochemical techniques.

  1. Photoinduced translational molecular mobility in solid nanostructured azo dye films

    SciTech Connect

    Ezhov, A A; Kozenkov, V M; Magnitskii, Sergey A; Nagorskii, Nikolay M; Panov, Vladimir I

    2011-11-30

    A new mechanism controlling the molecular motion in thin azo-containing films during a photoinduced change in the surface nanorelief is found. It is shown experimentally that exposure of a solid AD-1 azo dye, deposited on a glass substrate, to incoherent linearly polarised light leads to formation of nanostructures with a characteristic size of 200 nm, which are similar to droplets of melt of this dye on the same substrate. It is shown that photoinduced mass transport in a solid AD-1 azo dye film can be explained by the mobility of molecules related to their trans-cis-photoisomerisation, which leads to film softening with subsequent formation of spherical protrusions under surface tension forces.

  2. Dynamical properties of nucleus boundaries in photoinduced structural change

    NASA Astrophysics Data System (ADS)

    Ishida, Kunio; Nasu, Keiichiro

    2014-01-01

    Dynamics of the boundaries of photoinduced nuclei in electron-phonon systems is theoretically studied. By regarding the spatial distribution of the excited electronic state population as a geometric pattern, we applied the multifractal analysis to it and calculated the temporal behavior of the fractal dimension f(α) as a function of the Lipschitz-Hölder exponent α, which is an appropriate method for understanding the cooperative relaxation process of photoexcited states. We found that the incubation period observed in various types of photoinduced cooperative phenomena corresponds to the formation of embryonic nuclei which is driven by nonadiabatic/adiabatic transition between electronic states during the relaxation of the Franck-Condon state.

  3. [The natural history of 270 cases of Wolff-Parkinson-White syndrome in a survey of the general population].

    PubMed

    Soria, R; Guize, L; Chretien, J M; Le Heuzey, J Y; Lavergne, T; Desnos, M; Hagege, A; Guerre, Y

    1989-03-01

    Among 226,464 ambulatory subjects who underwent medical check-ups over a 15-year period, 270 were found to have Wolff-Parkinson-White syndrome (1.2 case in 1,000). The syndrome was more frequent in men (181 cases, 1.4 p. 1,000) than in women (89 cases, 0.9 p. 1,000). 222 subjects were aged from 20 to 49 years (1.4 p. 1,000) and only 48 were between 50 and 80 years of age (0.7 p. 1,000). 197 subjects were re-evaluated: 119 (60.4 p. 100) complained of palpitations and 78 (39.6 p. 100) were asymptomatic. Palpitations began at all ages, even after 50 years, and usually proceeded in short attacks lasting a few seconds or minutes, with a mean recurrence rate of 5 attacks per annum (76.4 p. 100). This constant pattern sometimes was interrupted for months or years. Conversely, in a minority of cases (23.5 p. 100) an unexpected accentuation occurred which lasted for hours or days. As years went by, palpitations tented to decrease and disappear. The pre-excitation area and its degree of fusion with the normal ventricular activation had no influence on the origin and frequency of palpitations. In contrast, sustained tachycardia seemed to be more frequent in cases with lateral and posterior left pre-excitation. Among 270 subjects with pre-excitation syndrome, 7 died including 4 whose death was not due to a cardiac disease, 2 who died suddenly and 1 who succumbed to ventricular tachycardia after a road accident. None of these patients had an associated heart disease. These last 3 cases might contribute to alter the usually favourable prognosis of Wolff-Parkinson-White syndrome.

  4. Catalytic synthesis of amides via aldoximes rearrangement.

    PubMed

    Crochet, Pascale; Cadierno, Victorio

    2015-02-14

    Amide bond formation reactions are among the most important transformations in organic chemistry because of the widespread occurrence of amides in pharmaceuticals, natural products and biologically active compounds. The Beckmann rearrangement is a well-known method to generate secondary amides from ketoximes. However, under the acidic conditions commonly employed, aldoximes RHC=NOH rarely rearrange into the corresponding primary amides RC(=O)NH2. In recent years, it was demonstrated that this atom-economical transformation can be carried out efficiently and selectively with the help of metal catalysts. Several homogeneous and heterogenous systems have been described. In addition, protocols offering the option to generate the aldoximes in situ from the corresponding aldehydes and hydroxylamine, or even from alcohols, have also been developed, as well as a series of tandem processes allowing the access to N-substituted amide products. In this Feature article a comprehensive overview of the advances achieved in this particular research area is presented.

  5. Modeling photoinduced fluorescence enhancement in semiconductor nanocrystal arrays

    NASA Astrophysics Data System (ADS)

    Maenosono, Shinya

    2003-07-01

    Photoinduced fluorescence enhancement (PFE) in semiconductor nanocrystal (NC) arrays is modeled based on the rate equations for ground-state, excited-state and photoionized NCs in the array. The photoionization process is broken down into fast and slow ionization processes, which are expected to relate to blinking and darkening phenomena, respectively. Consequently, PFE behavior is found to change drastically, as it depends on both the intrinsic properties of NCs, and on external conditions, such as surface-capping molecules and atmosphere.

  6. Vicinal Difluoroalkylation and Aminosulfonylation of Alkynes under Photoinduced Conditions.

    PubMed

    Xiang, Yuanchao; Li, Yuewen; Kuang, Yunyan; Wu, Jie

    2017-01-23

    A photoinduced vicinal difluoroalkylation and aminosulfonylation of alkynes under photocatalysis was realized. The combination of ethyl 2-bromo-2,2-difluoroacetate, alkynes, and DABCO⋅(SO2 )2 with hydrazines, catalyzed by 9-mes-10-methyl acridinium perchlorate in the presence of visible light, afforded (E)-ethyl 2,2-difluoro-4-aryl-4-sulfamoylbut-3-enoates in good yields with high stereoselectivity. This four-component reaction proceeds through radical addition with the insertion of sulfur dioxide.

  7. Polyyne synthesis using carbene/carbenoid rearrangements.

    PubMed

    Chalifoux, Wesley A; Tykwinski, Rik R

    2006-01-01

    Rearrangement of a carbene/carbenoid intermediate to form an acetylene moiety, known as the Fritsch-Buttenberg-Wiechell (FBW) rearrangement, was developed for the formation of polyynes and polyyne frameworks within highly conjugated organic materials. Necessary precursors can be prepared through formation of an alkynyl ketone, followed by dibromoolefination under Corey-Fuchs conditions. The carbenoid rearrangement is brought about by treatment of the dibromoolefin with BuLi under mild conditions. The success of these FBW reactions is quite solvent-dependent, and nonpolar hydrocarbon solvents (e.g., hexanes, toluene, benzene) work quite well, while use of ethereal solvents such as diethyl ether and tetrahydrofuran (THF) does not provide the desired polyyne product. This protocol was successfully applied to the formation of silyl, alkyl, alkenyl, and aryl polyynes, including di-, tri-, and tetrayne products, as well as the construction of two-dimensional carbon-rich molecules. A one-pot variant of this procedure is being developed and is particularly applicable toward the synthesis of polyyne natural products. Formation of a series of triisopropylsilyl end-capped polyynes, from the triyne to decayne, was achieved. Third-order nonlinear optical properties of these polyynes were evaluated. This study shows that the molecular second hyperpolarizabilities for the polyynes as a function of length increase at a rate that is higher than all other nonaromatic organic oligomers.

  8. The radical cation of anti-tricyclooctadiene and its rearrangement products

    PubMed

    Bally; Bernhard; Matzinger; Truttmann; Zhu; Roulin; Marcinek; Gebicki; Williams; Chen; Roth; Herbertz

    2000-03-03

    The anti dimer of cyclobutadiene (anti-tricyclo[4.2.0.0(2.5)]octa-3,7-diene, TOD) is subjected to ionization by gamma-irradiation in Freon matrices, pulse radiolysis in hydrocarbon matrices, and photoinduced electron transfer in solution. The resulting species are probed by optical and ESR spectroscopy (solid phase) as well as by CIDNP spectroscopy (solution). Thereby it is found that ionization of anti-TOD invariably leads to spontaneous decay to two products, that is bicyclo[4.2.0]octa-2,4,7-triene (BOT) and 1,4-dihydropentalene (1,4-DHP), whose relative yield strongly depends on the conditions of the experiment. Exploration of the C8H8*+ potential energy surface by the B3LYP/6-31G* density functional method leads to a mechanistic hypothesis for the observed rearrangements which involves a bifurcation between a pathway leading to the simple valence isomer, BOT*+, and another one leading to an unprecedented other valence isomer, the anti form of the bicyclo[3.3.0]octa-2,6-diene-4,8-diyl radical cation (anti-BOD*+). The latter product undergoes a very facile H-shift to yield the radical cation of 1,3a-dihydropentalene (1,3a-DHP*+) which ultimately rearrranges by a further H-shift to the observed product, 1,4-DHP*+.

  9. Structural analysis of a carcinogen-induced genomic rearrangement event

    SciTech Connect

    Barr, F.G.; Davis, R.J.; Eichenfield, L.; Emanuel, B.S. Univ. of Pennsylvania, Philadelphia )

    1992-02-01

    The authors have explored the mechanism of genomic rearrangement in a hamster fibroblast cell culture system in which rearrangements are induced 5{prime} to the endogenous thymidine kinase gene by chemical carcinogen treatment. The wild-type region around one rearrangement breakpoint was cloned and sequenced. With this sequence information, the carcinogen-induced rearrangement was cloned from the corresponding rearranged cell line by the inverse polymerase chain reaction. After the breakpoint fragment was sequenced, the wild-type rearrangement partner (RP15) was isolated by a second inverse polymerase chain reaction of unrearranged DNA. Comparison of the sequence of the rearrangement breakpoint with the wild-type RP15 and 5{prime} thymidine kinase gene regions revealed short repeats directly at the breakpoint, as well as nearby A+T-rich regions in rearrangement partner. Therefore, these studies reveal interesting sequence and chromatin features near the rearrangement breakpoints and suggest a role for nuclear organization in the mechanism of carcinogen-induced genomic rearrangement.

  10. Molecular Cytogenetic Analysis of Telomere Rearrangements

    PubMed Central

    Martin, Christa Lese; Ledbetter, David H.

    2015-01-01

    Genomic imbalances involving the telomeric regions of human chromosomes, which contain the highest gene concentration in the genome, are proposed to have severe phenotypic consequences. For this reason, it is important to identify telomere rearrangements and assess their contribution to human pathology. This unit describes the structure and function of human telomeres and outlines several FISH-based methodologies that can be employed to study these unique regions of human chromosomes. It is a revision of the original version of the unit published in 2000, now including an introductory section describing advances in the discipline that have taken place since the original publication. PMID:25599669

  11. Nonclassical 21-Homododecahedryl Cation Rearrangement Revisited.

    PubMed

    Jalife, Said; Mondal, Sukanta; Osorio, Edison; Cabellos, José Luis; Martínez-Guajardo, Gerardo; Fernández-Herrera, María A; Merino, Gabriel

    2016-03-04

    The degenerate rearrangement in the 21-homododecahedryl cation (1) has been studied via density functional theory computations and Born-Oppenheimer Molecular Dynamics simulations. Compound 1 can be described as a highly fluxional hyperconjugated carbocation. Complete scrambling of 1 can be achieved by the combination of two unveiled barrierless processes. The first one is a "rotation" of one of the six-membered rings via a 0.8 kcal·mol(-1) barrier, and the second one is a slower interconvertion between two hyperconjomers via an out-of-plane methine bending (ΔG(⧧) = 4.0 kcal·mol(-1)).

  12. Three-dimensional micro-level computational study of Wolff's law via trabecular bone remodeling in the human proximal femur using design space topology optimization.

    PubMed

    Boyle, Christopher; Kim, Il Yong

    2011-03-15

    The law of bone remodeling, commonly referred to as Wolff's Law, asserts that the internal trabecular bone adapts to external loadings, reorienting with the principal stress trajectories to maximize mechanical efficiency creating a naturally optimum structure. The goal of the current study was to utilize an advanced structural optimization algorithm, called design space optimization (DSO), to perform a micro-level three-dimensional finite element bone remodeling simulation on the human proximal femur and analyse the results to determine the validity of Wolff's hypothesis. DSO optimizes the layout of material by iteratively distributing it into the areas of highest loading, while simultaneously changing the design domain to increase computational efficiency. The result is a "fully stressed" structure with minimized compliance and increased stiffness. The large-scale computational simulation utilized a 175 μm mesh resolution and the routine daily loading activities of walking and stair climbing. The resulting anisotropic trabecular architecture was compared to both Wolff's trajectory hypothesis and natural femur samples from literature using a variety of visualization techniques, including radiography and computed tomography (CT). The results qualitatively revealed several anisotropic trabecular regions, that were comparable to the natural human femurs. Quantitatively, the various regional bone volume fractions from the computational results were consistent with quantitative CT analyses. The global strain energy proceeded to become more uniform during optimization; implying increased mechanical efficiency was achieved. The realistic simulated trabecular geometry suggests that the DSO method can accurately predict bone adaptation due to mechanical loading and that the proximal femur is an optimum structure as the Wolff hypothesized.

  13. Structures of Local Rearrangements in Soft Colloidal Glasses

    NASA Astrophysics Data System (ADS)

    Yang, Xiunan; Liu, Rui; Yang, Mingcheng; Wang, Wei-Hua; Chen, Ke

    2016-06-01

    We image local structural rearrangements in soft colloidal glasses under small periodic perturbations induced by thermal cycling. Local structural entropy S2 positively correlates with observed rearrangements in colloidal glasses. The high S2 values of the rearranging clusters in glasses indicate that fragile regions in glasses are structurally less correlated, similar to structural defects in crystalline solids. Slow-evolving high S2 spots are capable of predicting local rearrangements long before the relaxations occur, while fluctuation-created high S2 spots best correlate with local deformations right before the rearrangement events. Local free volumes are also found to correlate with particle rearrangements at extreme values, although the ability to identify relaxation sites is substantially lower than S2. Our experiments provide an efficient structural identifier for the fragile regions in glasses and highlight the important role of structural correlations in the physics of glasses.

  14. Photoinduced surface reactions on TiO{sub 2} and SrTiO{sub 3} films: Photocatalytic oxidation and photoinduced hydrophilicity

    SciTech Connect

    Miyauchi, Masahiro; Nakajima, Akira; Fujishima, Akira; Hashimoto, Kazuhito; Watanabe, Toshiya

    2000-01-01

    In the present study, the authors have evaluated photocatalytic activities and photoinduced wettabilities for TiO{sub 2} and SrTiO{sub 3} films. Although both types of films had almost the same photocatalytic oxidation activity, photoinduced wettabilities of these films showed different phenomena. The photoinduced hydrophilicity peculiar to TiO{sub 2} is not caused by the photocatalytic oxidation of organic compounds adsorbed on the surface. The highly hydrophilic surface of TiO{sub 2} is ascribed to photogenerated Ti{sup 3+} defect sites that are favorable for dissociative water absorption. The yield of this photoinduced hydrophilic reaction is not clear at the present time. It is noted that this reaction involves a surface structural change, which should not require a high quantum efficiency as compared to conventional photocatalytic oxidation.

  15. Photoinduced ordering and anchoring properties of azo-dye films.

    PubMed

    Kiselev, Alexei D; Chigrinov, Vladimir; Huang, Dan Ding

    2005-12-01

    We study both theoretically and experimentally the anchoring properties of photoaligning azo-dye films in contact with a nematic liquid crystal depending on the photoinduced ordering of azo-dye molecules. In the mean field approximation, we found that the bare surface anchoring energy depends linearly on the azo-dye order parameter and the azimuthal anchoring strength decays to zero in the limit of vanishing photoinduced ordering. From the absorption dichroism spectra measured in azo-dye films that are prepared from an azo-dye derivative with polymerizable terminal groups we obtain the dependence of the dichroic ratio on the irradiation dose. We also measure the polar and azimuthal anchoring strengths in nematic liquid crystal (NLC) cells aligned by the azo-dye films and derive the anchoring strengths as functions of the dichroic ratio, which is proportional to the photoinduced order parameter. Although linear fitting of the experimental data for both anchoring strengths gives reasonable results, it, predicts vanishing of the azimuthal anchoring strength at some nonzero value of the azo-dye order parameter, in contradiction with theory. By using a simple phenomenological model we show that this discrepancy can be attributed to the difference between the surface and bulk order parameters in the films. The measured polar anchoring energy is found to be an order of magnitude higher than the azimuthal strength. Our theory suggests that the quadrupole term of the spherical harmonics expansion for the azo-dye-NLC intermolecular potential might be of importance for the understanding of this difference.

  16. Molecular refinement of gibbon genome rearrangements.

    PubMed

    Roberto, Roberta; Capozzi, Oronzo; Wilson, Richard K; Mardis, Elaine R; Lomiento, Mariana; Tuzun, Eray; Cheng, Ze; Mootnick, Alan R; Archidiacono, Nicoletta; Rocchi, Mariano; Eichler, Evan E

    2007-02-01

    The gibbon karyotype is known to be extensively rearranged when compared to the human and to the ancestral primate karyotype. By combining a bioinformatics (paired-end sequence analysis) approach and a molecular cytogenetics approach, we have refined the synteny block arrangement of the white-cheeked gibbon (Nomascus leucogenys, NLE) with respect to the human genome. We provide the first detailed clone framework map of the gibbon genome and refine the location of 86 evolutionary breakpoints to <1 Mb resolution. An additional 12 breakpoints, mapping primarily to centromeric and telomeric regions, were mapped to approximately 5 Mb resolution. Our combined FISH and BES analysis indicates that we have effectively subcloned 49 of these breakpoints within NLE gibbon BAC clones, mapped to a median resolution of 79.7 kb. Interestingly, many of the intervals associated with translocations were gene-rich, including some genes associated with normal skeletal development. Comparisons of NLE breakpoints with those of other gibbon species reveal variability in the position, suggesting that chromosomal rearrangement has been a longstanding property of this particular ape lineage. Our data emphasize the synergistic effect of combining computational genomics and cytogenetics and provide a framework for ultimate sequence and assembly of the gibbon genome.

  17. Photoinduced electron transfer across molecular bridges: electron- and hole-transfer superexchange pathways.

    PubMed

    Natali, Mirco; Campagna, Sebastiano; Scandola, Franco

    2014-06-21

    Photoinduced electron transfer plays key roles in many areas of chemistry. Superexchange is an effective model to rationalize photoinduced electron transfer, particularly when molecular bridges between donor and acceptor subunits are present. In this tutorial review we discuss, within a superexchange framework, the complex role played by the bridge, with an emphasis on differences between thermal and photoinduced electron transfer, oxidative and reductive photoinduced processes, charge separation and charge recombination. Modular bridges are also considered, with specific attention to the distance dependence of donor-acceptor electronic coupling and electron transfer rate constants. The possibility of transition, depending on the bridge energetics, from coherent donor-acceptor electron transfer to incoherent charge injection and hopping through the bridge is also discussed. Finally, conceptual analogies between bridge effects in photoinduced electron transfer and optical intervalence transfer are outlined. Selected experimental examples, instrumental to illustration of the principles, are discussed.

  18. Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

    PubMed Central

    Hare, Stephanie R

    2016-01-01

    Summary This review describes unexpected dynamical behaviors of rearranging carbocations and the modern computational methods used to elucidate these aspects of reaction mechanisms. Unique potential energy surface topologies associated with these rearrangements have been discovered in recent years that are not only of fundamental interest, but also provide insight into the way Nature manipulates chemical space to accomplish specific chemical transformations. Cautions for analyzing both experimental and theoretical data on carbocation rearrangements are included throughout. PMID:27340434

  19. Photoinduced underwater superoleophobicity of TiO2 thin films.

    PubMed

    Sawai, Yusuke; Nishimoto, Shunsuke; Kameshima, Yoshikazu; Fujii, Eiji; Miyake, Michihiro

    2013-06-11

    The photoinduced wettabilities of water, n-hexadecane, dodecane, and n-heptane on a flat TiO2 surface prepared by a sol-gel method-based coating were investigated. An amphiphilic surface produced by UV irradiation exhibited underwater superoleophobicity with an extremely high static oil contact angle (CA) of over 160°. The TiO2 surface almost completely repelled the oil droplet in water. A robust TiO2 surface with no fragile nanomicrostructure was fabricated on a Ti mesh with a pore size of approximately 150 μm. The fabricated mesh was found to be applicable as an oil/water separation filter.

  20. Distance dependence in photo-induced intramolecular electron transfer

    NASA Astrophysics Data System (ADS)

    Larsson, Sven; Volosov, Andrey

    1986-09-01

    The distance dependence of the rate of photo-induced electron transfer reactions is studied. A quantum mechanical method CNDO/S is applied to a series of molecules recently investigated by Hush et al. experimentally. The calculations show a large interaction through the saturated bridge which connects the two chromophores. The electronic matrix element HAB decreases a factor 10 in about 4 Å. There is also a decrease of the rate due to less exothermicity for the longer molecule. The results are in fair agreement with the experimental results.

  1. Photo-induced transmittance in copper selenide nanowires

    NASA Astrophysics Data System (ADS)

    Statkutė, G.; Mikulskas, I.; Jagminas, A.; Tomašiūnas, R.

    2008-01-01

    Photo-induced transmission was investigated in Cu 1.7Se nanowires electrochemically deposited in alumina matrix pores with a central channel of the diameters of 12, 15 and 60 nm by means of the degenerate picosecond pump-probe technique at 1.064 μm wavelength. Resonant excitation intensity dependencies were interpreted. Absorption saturation was ascertained as a result of the drain of acceptor shallow centers. The estimated absorption cross-section was 10 -12 cm 2, saturation intensity - was 1-10 mJ cm -2.

  2. Photoinduced electron transfer based ion sensing within an optical fiber.

    PubMed

    Englich, Florian V; Foo, Tze Cheung; Richardson, Andrew C; Ebendorff-Heidepriem, Heike; Sumby, Christopher J; Monro, Tanya M

    2011-01-01

    We combine suspended-core microstructured optical fibers with the photoinduced electron transfer (PET) effect to demonstrate a new type of fluorescent optical fiber-dip sensing platform for small volume ion detection. A sensor design based on a simple model PET-fluoroionophore system and small core microstructured optical fiber capable of detecting sodium ions is demonstrated. The performance of the dip sensor operating in a high sodium concentration regime (925 ppm Na(+)) and for lower sodium concentration environments (18.4 ppm Na(+)) is explored and future approaches to improving the sensor's signal stability, sensitivity and selectivity are discussed.

  3. Applications of the Wittig-Still rearrangement in organic synthesis.

    PubMed

    Rycek, Lukas; Hudlicky, Tomas

    2017-02-16

    This review traces the discovery of the Wittig-Still rearrangement and its applications in organic synthesis. Its relationship to Wittig rearrangements is discussed along with detailed analysis of E/Z- and diastereoselectivity. Modifications of the products arising from the Wittig-Still rearrangement are reviewed in the context of increased complexity in intermediates potentially useful in target oriented synthesis. Early applications of the Wittig-Still rearrangement to modifications of steroids are reviewed as are applications to various terpene and alkaloid natural product targets and miscellaneous compounds. To the best of our knowledge, the literature is covered through December 2016.

  4. Accuracy of the Electrocardiogram in Localizing the Accessory Pathway in Patients with Wolff-Parkinson-White Pattern

    PubMed Central

    Teixeira, Carlos Manuel; Pereira, Telmo António; Lebreiro, Ana Margarida; Carvalho, Sérgio Alexandre

    2016-01-01

    Background There are currently several electrocardiographic algorithms to locate the accessory pathway (AP) in patients with Wolff-Parkinson-White (WPW) syndrome. Objective To compare the ability of electrocardiographic algorithms in identifying the location of the AP in patients with WPW pattern referred for ablation. Methods Observational, cross-sectional, retrospective study with 111 patients with WPW syndrome referred for AP ablation. The electrocardiogram (ECG) obtained prior to the ablation was analyzed by an experienced observer who consecutively applied seven algorithms to identify non-invasively the AP. We then compared the location estimated with this assessment with that obtained in the electrophysiological study and calculated the agreement rates. Results Among the APs, 59 (53.15%) were distributed around the mitral annulus and the remaining 52 (46.85%) were located around the tricuspid annulus. The overall absolute accuracy of the algorithms evaluated varied between 27% and 47%, increasing to between 40% and 76% when we included adjacent locations. The absolute agreement rate by AP location was 2.00-52.20% for septal APs (n = 51), increasing to 5.90-90.20% when considering adjacent locations; 7.70-69.20% for right APs (n = 13), increasing to 42.90-100% when considering adjacent locations; and 21.70-54.50% for left APs (n = 47), increasing to 50-87% when considering adjacent locations. Conclusion The agreement rates observed for the analyzed scores indicated a low discriminative ability of the ECG in locating the AP in patients with WPW. PMID:27627222

  5. [Influence of exercise on the permeability of accessory pathways and supraventricular arrhythmia in Wolff-Parkinson-White syndrome].

    PubMed

    Mabo, P; Kermarrec, A; Gras, D; Paillard, F; Bédossa, M; Daubert, C

    1992-10-01

    The influence of adrenergic stimulation on the effective anterograde refractory period of the accessory pathways and on supraventricular arrhythmias, was studied in 20 patients (average age 38 +/- 16 years) with an untreated permanent Wolff-Parkinson-White syndrome and a resting anterograde refractory period < or = 400ms. Repeated electrophysiological studies with a single endocavity catheter positioned near the atrial pole of the accessory pathway were performed under basal conditions and during a standardised exercise test on a bicycle ergometer. The effective anterograde refractory period of the accessory pathway, the length of the tachycardia cycle during reciprocating orthodromic tachycardia, the average heart rate, the percentage of preexcited QRS complexes during induced atrial fibrillation, were measured in all patients under basal conditions and at the peak of exercise. Exercise significantly reduced the anterograde refractory period of the accessory pathway (287 +/- 49 ms at rest versus 238 +/- 24 ms on exercise: p < 0.001), the cycle of orthodromic tachycardia (302 +/- 32 vs 260 +/- 22 ms p < 0.001), the minimal R-R interval (270 +/- 65 vs 227 +/- 46 ms: p < 0.05) and % of preexcited QRS complexes (75 +/- 33 vs 51 +/- 39: p < 0.05) in atrial fibrillation whilst increasing the average heart rate (165 +/- 42 vs 202 +/- 39 bpm: p < 0.02). Adrenergic stimulation significantly improves anterograde conduction in the accessory pathway. The reduction in the % of preexcited QRS complexes in atrial fibrillation could indicate a preferential action of catecholamines on the nodo-hisian pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. [Wolff-Parkinson-White syndrome. Outcome of patients treated with anti-arrhythmia agents from data of electrophysiological examinations].

    PubMed

    Cointe, R; Lévy, S; Metge, M; Bru, P; Bricaud, H; Gérard, R

    1988-02-01

    Seventy-two consecutive patients with electrocardiographic evidence of Wolff-Parkinson-White syndrome underwent electrophysiological study (EPS). Fifty-five of these patients (76 p. 100) had episodes of tachycardia, 11 experienced palpitations or syncopes and 6 were asymptomatic. The decision to prescribe an antiarrhythmic agent was reached on the basis of the patients' symptoms and EPS data. One patient was treated by surgery before the medical treatment was tried; 17 patients were discharged without treatment, 4 were discharged with an episodic and 50 with a preventive antiarrhythmic treatment. Among these 50 patients, 46 (92 p. 100) could be followed up for a mean period of 45.7 +/- 28 months. One died of lung cancer; 43 presented with spontaneous episodes of tachycardia, 4 were able to discontinue treatment at the end of the follow-up period since they had very few symptoms and 2 were lost sight of. Among the 37 patients under antiarrhythmic treatment followed up, 29 (78 p. 100) are well controlled, while 8 (22 p. 100) still present with episodes of tachycardia. A tachycardia-reducing pacemaker was implanted in 5 of these 8 patients. It therefore appears that 78 p. 100 of patients presenting with spontaneous episodes of tachycardia associated with WPW syndrome can be controlled with an antiarrhythmic treatment. This result was obtained after trying at least two types of antiarrhythmic agents in 86 p. 100 of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

  7. [Difficulties of persistent repolarization following normalization of the QRS wave in the Wolff-Parkinson-White syndrome].

    PubMed

    Laham, J; Frank, R; Fontaine, G; Artigou, Y; Heller, J; Gerbaux, A; Grosgogeat, Y

    1982-06-01

    The normalisation of the ventricular complex in the Wolff-Parkinson-White syndrome is often accompanied by changes in the repolarisation phase with a deep, symmetric and pointed T wave suggestive of coronary artery disease. In order to study this phenomenon we examined 29 cases of intermittent WPW, 13 of which had abnormalities of the normalised complex. Normalisation occurred spontaneously on 10 occasions, twice on exercise and once after Ajmaline. In the majority of cases (9/13) the preexcitation was a right (4 cases) or left (5 cases) posterior pathway and the T waves were abnormal in the posterior leads (II, III and AVF). In left lateral preexcitation the T waves were negative in lead 1 and AVL. The T wave changes seem to be related to the topography of the preexcitation pathway. They gradually disappeared in the 3 cases in which preexcitation had not recurred. The age of the patients (11 to 45 years, average 31 years) or normal coronary angiography, performed in 3 cases, excluded coronary pathology as did the close relationship between the topography of the preexcitation and the T wave changes and the gradual disappearance of the abnormalities in the cases where preexcitation did not recur. This phenomenon, related to abnormal ventricular activation, seems to be comparable to the changes in ventricular repolarisation observed on termination of ventricular pacing, on the regression of certain intermittent left bundle branch blocks and perhaps, in some cases, of the post-ventricular tachycardia syndrome.

  8. [Influence of age on the presumed cause of syncope in patients with the Wolff-Parkinson-White syndrome].

    PubMed

    Chometon, F; Brembilla-Perrot, B

    2007-01-01

    The aim of this study was to assess the causes of syncope in patients with the Wolff-Parkinson-White syndrome (WPW) and to determine whether the age of the patients was a significant factor. Forty-seven patients with a WPW, aged 11 to 72 years, underwent electrophysiological study by the oesophageal approach because of an unexplained syncope. Nineteen patients were under 20 years of age (16 +/- 3 years: group I) and 28 were over 20 years of age (40 +/- 13 years: group II). Junctional tachycardia was induced in 8 patients of group I (42%) and in 13 of group II (46%) (NS); atrial fibrillation was induced in 8 patients of group I (42%) and in 9 of group II (35%) (NS). A potentially malignant form of WPW was identified in 8 patients of group I (42%) and in 11 of group II (39%) (NS); Syncope was directly attributed to the WPW in 14 patients of group I (74%) and in 19 of group II (78%), either after identification of a serious form or induction of junctional tachycardia (6 patients of group I and 8 of group II). The rest of the syncopal episodes had various causes. There were no deaths. The authors conclude that oesophageal electrophysiological investigations enable rapid identification of a high incidence of tachycardias probably responsible for syncope in WPW. The causes of syncope and incidence of potentially severe forms of WPW were not significantly influenced by the age of the patients.

  9. Photoinduced Birefringence in Azo-Dye Doped Polyurethane

    NASA Astrophysics Data System (ADS)

    Aleksejeva, J.; Gerbreders, A.; Reinfelde, M.; Teteris, J.

    2011-01-01

    In this report we describe a photoinduced birefringence in disperse red (DR1) azo-dye doped polyurethane films. DR1 dye molecules in these films are chemically bound with the polyurethane polymer's main chain. Under laser radiation the DR1 molecules experience the isomerization process; as a result, the dipole moment of such a molecule changes and they align in the presence of electric field. Photo-birefringence was induced by linearly polarized laser radiation (532 nm, 448 nm, 375 nm and 632.8 nm) in the films with various concentrations of DR1 dye. The photo-induced birefringence (PIBR) Δn was measured at 634 nm wavelength, and its dependences on the pumping beam wavelength and intensity were evaluated. The Δn relaxation was studied both in the dark and under light illumi-nation. In DR1-doped polyurethane films the holographic recording was performed using laser light radiation (532 nm). The profile of surface relief grating (SRG) was studied using AFM. The relationship between SRG formation and PIBR is discussed.

  10. Photo-induced Mass Transport through Polymer Networks

    NASA Astrophysics Data System (ADS)

    Meng, Yuan; Anthamatten, Mitchell

    2014-03-01

    Among adaptable materials, photo-responsive polymers are especially attractive as they allow for spatiotemporal stimuli and response. We have recently developed a macromolecular network capable of photo-induced mass transport of covalently bound species. The system comprises of crosslinked chains that form an elastic network and photosensitive fluorescent arms that become mobile upon irradiation. We form loosely crosslinked polymer networks by Michael-Addition between multifunctional thiols and small molecule containing acrylate end-groups. The arms are connected to the network by allyl sulfide, that undergoes addition-fragmentation chain transfer (AFCT) in the presence of free radicals, releasing diffusible fluorophore. The networks are loaded with photoinitiator to allow for spatial modulation of the AFCT reactions. FRAP experiments within bulk elastomers are conducted to establish correlations between the fluorophore's diffusion coefficient and experimental variables such as network architecture, temperature and UV intensity. Photo-induced mass transport between two contacted films is demonstrated, and release of fluorophore into a solvent is investigated. Spatial and temporal control of mass transport could benefit drug release, printing, and sensing applications.

  11. Model for photoinduced bending of slender molecular crystals.

    PubMed

    Nath, Naba K; Pejov, Ljupčo; Nichols, Shane M; Hu, Chunhua; Saleh, Na'il; Kahr, Bart; Naumov, Panče

    2014-02-19

    The growing realization that photoinduced bending of slender photoreactive single crystals is surprisingly common has inspired researchers to control crystal motility for actuation. However, new mechanically responsive crystals are reported at a greater rate than their quantitative photophysical characterization; a quantitative identification of measurable parameters and molecular-scale factors that determine the mechanical response has yet to be established. Herein, a simple mathematical description of the quasi-static and time-dependent photoinduced bending of macroscopic single crystals is provided. This kinetic model goes beyond the approximate treatment of a bending crystal as a simple composite bilayer. It includes alternative pathways for excited-state decay and provides a more accurate description of the bending by accounting for the spatial gradient in the product/reactant ratio. A new crystal form (space group P21/n) of the photoresponsive azo-dye Disperse Red 1 (DR1) is analyzed within the constraints of the aforementioned model. The crystal bending kinetics depends on intrinsic factors (crystal size) and external factors (excitation time, direction, and intensity).

  12. Photo-induced reduction of flavin mononucleotide in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Song, S.-H.; Dick, B.; Penzkofer, A.

    2007-01-01

    The photo-induced reduction of flavin mononucleotide (FMN) in aqueous solutions is studied by absorption spectra measurement under aerobic and anaerobic conditions. Samples without exogenous reducing agent and with the exogenous reducing agents ethylene-diamine-tetraacetic acid (EDTA) and dithiothreitol (DTT) are investigated. Under anaerobic conditions the photo-induced reduction with and without reducing agents is irreversible. Under aerobic conditions the photo-reduction without added reducing agent is small compared to the photo-degradation, and the photo-reduction of FMN by the reducing agents is reversible (re-oxidation in the dark). During photo-excitation of FMN the dissolved oxygen is consumed by singlet oxygen formation and subsequent chemical reaction. After light switch-off slow re-oxidation (slow absorption recovery) occurs due to air in-diffusion from surface. EDTA degradation by FMN excitation leads to oxygen scavenging. The quantum efficiencies of photo-reduction under aerobic and anaerobic conditions are determined. The re-oxidation of reduced FMN under aerobic conditions and due to air injection is investigated.

  13. Photoinduced development of antibacterial materials derived from isosorbide moiety.

    PubMed

    Lorenzini, Cedric; Haider, Adnan; Kang, Inn-Kyu; Sangermano, Marco; Abbad-Andalloussi, Samir; Mazeran, Pierre-Emmanuel; Lalevée, Jacques; Renard, Estelle; Langlois, Valérie; Versace, Davy-Louis

    2015-03-09

    A straightforward method for immobilizing in situ generated silver nanoparticles on the surface of a photoactivable isosorbide-derived monomer is developed with the objective to design a functional material having antibacterial properties. The photoinduced thiol-ene mechanism involved in these syntheses is described by the electron spin resonance/spin trapping technique. The resulting materials with or without silver nanoparticles (Ag NPs) were used as films or as coatings on glass substrate. The surface of the synthesized materials was characterized by X-ray photoelectron spectroscopy and scanning electron microscopy, and their thermal and mechanical properties were evaluated by dynamic-mechanical thermal tests, differential scanning calorimetry, thermogravimetric analyses, along with pencil hardness, nanoindentation, and scratch resistance tests. The photoinduced formation of Ag NPs is also confirmed by UV spectrophotometry. Finally, a primary investigation demonstrates the antibacterial properties of the isosorbide-derived material against Staphylococcus aureus and Escherichia coli, as well as its cytocompatibility toward NIH 3T3 fibroblastic cells.

  14. Photoinduced giant magnetic polarons in EuTe

    NASA Astrophysics Data System (ADS)

    Henriques, A. B.; Naupa, A. R.; Usachev, P. A.; Pavlov, V. V.; Rappl, P. H. O.; Abramof, E.

    2017-01-01

    Photoinduced magnetic polarons in EuTe, with a magnetic moment of several hundred Bohr magnetons, were investigated as a function of pump intensity and temperature by pump-probe Faraday rotation. The quantum efficiency for optical generation of magnetic polarons is found to be 0.09. The pump-intensity dependence of the photoinduced Faraday rotation shows a sublinear increase, from which we deduce that the population of photoexcited polarons is limited by a maximum value of 4.5 ×1015cm-3 . This is four orders of magnitude less than the concentration of polarons that would completely fill the crystal, which suggests that the photoexcited polarons are anchored by defects. In addition to the generation of polarons, at high pump densities the modulated pump light also causes a small alternating heating of the illuminated region. The temperature dependence of the polaron magnetic moment is well described by the Curie-Weiss law. Above 100 K, polarons are thermally quenched with an activation energy of 11 meV.

  15. Photoinduced Kondo effect in CeZn3P3

    NASA Astrophysics Data System (ADS)

    Kitagawa, J.; Kitajima, D.; Shimokawa, K.; Takaki, H.

    2016-01-01

    The Kondo effect, which originates from the screening of a localized magnetic moment by a spin-spin interaction, is widely observed in nonartificial magnetic materials, artificial quantum dots, and carbon nanotubes. In devices based on quantum dots or carbon nanotubes that target quantum information applications, the Kondo effect can be tuned by a gate voltage, a magnetic field, or light. However, the manipulation of the Kondo effect in nonartificial materials has not been thoroughly studied; in particular, the artificial creation of the Kondo effect remains unexplored. Per this subject study, however, a route for the optical creation of the Kondo effect in the nonartificial material p -type semiconductor CeZn3P3 is presented. The Kondo effect emerges under visible-light illumination of the material by a continuous-wave laser diode and is ultimately revealed by photoinduced electrical resistivity, which clearly exhibits a logarithmic temperature dependency. By contrast, a La-based compound (LaZn3P3 ) displays only normal metallic behavior under similar illumination. The photoinduced Kondo effect, which occurs at higher temperatures when compared with the Kondo effect in artificial systems, provides a potential range of operation for not only quantum information/computation devices but also for operation of magneto-optic devices, thereby expanding the range of device applications based on the Kondo effect.

  16. Imaging of photoinduced tautomerism in single porphyrin molecules

    NASA Astrophysics Data System (ADS)

    Jäger, Regina; Chizhik, Anna M.; Chizhik, Alexey I.; Mack, Hans-Georg; Lyubimtsev, Alexey; Hanack, Michael; Meixner, Alfred J.

    2011-10-01

    In this work we present our new experimental and theoretical results upon investigations of the photoinduced tautomerism processes of single metal-free porphyrin-type molecules. During tautomerization a molecule changes its structure, therefore the excitation transition dipole moment (TDM) of the molecule changes its orientation. Using confocal microscopy in combination with azimuthally and radially polarized laser beams we are able to determine the orientation of the TDM as well as the orientation of a single molecule itself. In the case of tautomerism we are able to visualize this process and even the involved isomers separately. The study first focuses on two symmetrical compounds: a phthalocyanine and a porphyrin. Additionally, differences of the single molecules embedded in a polymer matrix or just spin-coated on a glass cover slide and under nitrogen flow are investigated. In the latter case we observe a higher frequency of the change of the TDM orientation. The experimental studies are supplemented by quantum chemical calculations. Variations of the molecular substituents, the environment and excitation wavelength can give new insights into the excited-state tautomerism process of a single molecule. We also introduce some suggestions for future experiments to support the understanding of the photoinduced tautomerism.

  17. Photoinduced Electron Transfer Process Visualized on Single Silver Nanoparticles.

    PubMed

    Lei, Gang; Gao, Peng Fei; Yang, Tong; Zhou, Jun; Zhang, Hong Zhi; Sun, Shan Shan; Gao, Ming Xuan; Huang, Cheng Zhi

    2017-02-28

    Understanding the photoinduced electron transfer (PET) mechanism is vital to improving the photoelectric conversion efficiency for solar energy materials and photosensitization systems. Herein, we visually demonstrate the PET process by real-time monitoring the photoinduced chemical transformation of p-aminothiophenol (p-ATP), an important SERS signal molecule, to 4,4'-dimercaptoazobenzene on single silver nanoparticles (AgNPs) with a localized surface plasmon resonance (LSPR) spectroscopy coupled dark-field microscopy. The bidirectional LSPR scattering spectral shifts bathochromically at first and hypsochromically then, which are caused by the electron transfer delay of p-ATP, disclose the PET path from p-ATP to O2 through AgNPs during the reaction, and enable us to digitalize the corresponding electron loss and gain on the surface of AgNP at different time periods. This visualized PET process could provide a simple and efficient approach to explore the nature of PET and help to interpret the SERS mechanism in terms of p-ATP.

  18. Millisecond Photoinduced Absorption Studies of Pyridine-Based Copolymer Films

    NASA Astrophysics Data System (ADS)

    Coplin, K. A.; Clark, D. T.; Jessen, S. W.; Epstein, A. J.; Fu, D.-K.; Swager, T. M.

    1997-03-01

    We present a study of the photoexcited states in copolymers of poly(p-pyridyl vinylene) and poly(p-phenylene vinylene) (PPyVPR_iV) with sidegroups R_1=C_12H_25 or R_2=COOC_12H_25 attached at the 2 and 5 positions of the phenyl ring. Previous studies discussed the millisecond photoinduced absorption (ms PA) characteristics of PPyVPR_iV powders(S.W. Jessen et al.), Synth. Met., in press.. In particular, triplet-triplet (T-T) transitions were observed at 1.6 eV for both materials. Additional polaron signatures were also observed in both the electronic ( ~ 0.85 eV) and infrared (1100 - 1600 cm-1) regions of the photoinduced spectrum. We compare these powder results with ms PA features for film morphologies of both the copolymers. We observe a weaker ( ~ 10X) T-T^* transition for copolymer films cast from xylene solution indicating a reduction in triplet exciton production as compared to powder samples. These results are contrasted with the behavior we reported(S.W. Jessen et al.), to be published. earlier for film and powder samples of the parent polymer poly(p-pyridyl vinylene).

  19. Cytoplasmic rearrangements associated with amphibian egg symmetrization

    NASA Technical Reports Server (NTRS)

    Malacinski, G. M.

    1984-01-01

    Cytoplasmic rearrangements which follow fertilization were mentioned in normal and inverted eggs. A set of yolk compartments was resolved by cytological analyses of both normally oriented and inverted eggs. Those compartments were characterized by their yolk platelet compositions and movement during egg inversion. It is found that during egg inversion the yolk compartments shift minor cytoplasmic compartments which line the egg cortex. Those yolk mass shifts occurred only after the inverted egg was activated. The direction of shift of the major yolk components, rather than the sperm entrance site, determines the dorsal/ventral polarity of the inverted egg. Among different spawnings the rate of shift varied. Eggs that displayed the fastest rate of shift exhibited the highest frequency of developmental abnormalities during organogenesis. Interpretation of novel observations on cytoplasmic organization provide criticism of some earlier models. A new density compartment model is presented as a coherent way to view the organization of the egg cytoplasm and the development of bilateral symmetry.

  20. Androgen receptor gene mutation, rearrangement, polymorphism

    PubMed Central

    Eisermann, Kurtis; Wang, Dan; Jing, Yifeng; Pascal, Laura E.

    2013-01-01

    Genetic aberrations of the androgen receptor (AR) caused by mutations, rearrangements, and polymorphisms result in a mutant receptor that has varied functions compared to wild type AR. To date, over 1,000 mutations have been reported in the AR with most of these being associated with androgen insensitivity syndrome (AIS). While mutations of AR associated with prostate cancer occur less often in early stage localized disease, mutations in castration-resistant prostate cancer (CRPC) patients treated with anti-androgens occur more frequently with 10-30% of these patients having some form of mutation in the AR. Resistance to anti-androgen therapy usually results from gain-of-function mutations in the LBD such as is seen with bicalutamide and more recently with enzalutamide (MDV3100). Thus, it is crucial to investigate these new AR mutations arising from drug resistance to anti-androgens and other small molecule pharmacological agents. PMID:25045626

  1. Synthesis of Methyl Cyclopentanecarboxylate: A Laboratory Experience in Carbon Rearrangement

    ERIC Educational Resources Information Center

    Orchard, Alexandra; Maniquis, Roxanne V.; Salzameda, Nicholas T.

    2016-01-01

    We present a novel guided inquiry second semester organic chemistry laboratory rearrangement experiment. Students performed the Favorskii Rearrangement to obtain methyl cyclopentanecarboxylate in good yields. The students learned about the individual steps of the Favorskii mechanism and were required to propose a complete reaction mechanism and…

  2. Kinetics of photoinduced anisotropy in bacteriorhodopsin film under two pumping beams.

    PubMed

    Han, Junhe; Yao, Baoli; Gao, Peng; Chen, Liju; Wang, Yingli; Lei, Ming

    2008-07-20

    Photoinduced anisotropy in bacteriorhodopsin (BR) film arises from the selective bleaching of BR molecules to linearly polarized light. The kinetics of photoinduced anisotropy excited by single and two pumping beams are investigated theoretically and experimentally. Compared with a single pumping beam (650 nm), which produces comparatively small photoinduced anisotropy, dual-wavelength linearly polarized pumping beams (650 and 405 nm) can obviously change the photoinduced anisotropy. When the polarization orientation of the 405 nm pumping beam is perpendicular to that of the 650 nm pumping beam, the peak and steady values of the photoinduced anisotropy kinetic curves are remarkably enhanced. But when the two pumping beams have parallel polarization orientation, the peak and steady values are restrained. At a fixed intensity of the 650 nm pumping beam, there exists an optimal intensity for the 405 nm pumping beam to maximize the value of the photoinduced anisotropy. The photoinduced transmittance of the polarizer-BR-analyzer system is modulated by the polarization angle of the 405 nm pumping beam in an approximate-cosine form.

  3. Photoinduced currents in pristine and ion irradiated kapton-H polyimide

    SciTech Connect

    Sharma, Anu Sridharbabu, Y. Quamara, J. K.

    2014-10-15

    The photoinduced currents in pristine and ion irradiated kapton-H polyimide have been investigated for different applied electric fields at 200°C. Particularly the effect of illumination intensity on the maximum current obtained as a result of photoinduced polarization has been studied. Samples were irradiated by using PELLETRON facility, IUAC, New Delhi. The photo-carrier charge generation depends directly on intensity of illumination. The samples irradiated at higher fluence show a decrease in the peak current with intensity of illumination. The secondary radiation induced crystallinity (SRIC) is responsible for the increase in maximum photoinduced currents generated with intensity of illumination.

  4. Biotinylated Platinum(II) Ferrocenylterpyridine Complexes for Targeted Photoinduced Cytotoxicity.

    PubMed

    Mitra, Koushambi; Shettar, Abhijith; Kondaiah, Paturu; Chakravarty, Akhil R

    2016-06-06

    Biotinylated platinum(II) ferrocenylterpyridine (Fc-tpy) complexes [Pt(Fc-tpy)(L(1))]Cl (1) and [Pt(Fc-tpy)(L(2))]Cl (2), where HL(1) and HL(2) are biotin-containing ligands, were prepared, and their targeted photoinduced cytotoxic effect in cancer cells over normal cells was studied. A nonbiotinylated complex, [Pt(Fc-tpy)(L(3))]Cl (3), was prepared as a control to study the role of the biotin moiety in cellular uptake properties of the complexes. Three platinum(II) phenylterpyridine (Ph-tpy) complexes, viz., [Pt(Ph-tpy)(L(1))]Cl (4), [Pt(Ph-tpy)(L(2))]Cl (5), and [Pt(Ph-tpy)(L(3))]Cl (6), were synthesized and explored to understand the role of a metal-bound Fc-tpy ligand over Ph-tpy as a photoinitiator. The Fc-tpy complexes displayed an intense absorption band near 640 nm, which was absent in their Ph-tpy analogues. The Fc-tpy complexes (1 mM in 0.1 M TBAP) showed an irreversible cyclic voltammetric anodic response of the Fc/Fc(+) couple near 0.25 V. The Fc-tpy complexes displayed photodegradation in red light of 647 nm involving the formation of a ferrocenium ion (Fc(+)) and reactive oxygen species (ROS). Photoinduced release of the biotinylated ligands was observed from spectral measurements, and this possibly led to the controlled generation of an active platinum(II) species, which binds to the calf-thymus DNA used for this study. The biotinylated photoactive Fc-tpy complexes showed significant photoinduced cytotoxicity, giving a IC50 value of ∼7 μM in visible light of 400-700 nm with selective uptake in BT474 cancer cells over HBL-100 normal cells. Furthermore, ferrocenyl complexes resulted in light-induced ROS-mediated apoptosis, as indicated by DCFDA, annexin V/FITC staining, and sub-G1 DNA content determined by fluorescent activated cell sorting analysis. The phenyl analogues 4 and 5 were photostable, served as DNA intercalators, and demonstrated selective cytotoxicity in the cancer cells, giving IC50 values of ∼4 μM.

  5. Exercise testing and thallium-201 myocardial perfusion scintigraphy in the clinical evaluation of patients with Wolff Parkinson White syndrome

    SciTech Connect

    Poyatos, M.E.; Suarez, L.; Lerman, J.; Guibourg, H.; Camps, J.; Perosio, A.

    1986-10-01

    In 58 patients with Wolff Parkinson White syndrome (WPW), we performed exercise stress testing in order to investigate the incidence of normalization of the auriculo-ventricular conduction and the ST-segment changes. For a more accurate evaluation of the latter, exercise and redistribution radionuclide images with Thallium-201 were obtained in 18 cases. Forty-nine had type A and nine had type B of WPW. Forty-eight had permanent, four had alternant and six had no pre-excitation (PE) when they started the test. Mean maximal functional capacity, mean maximal heart rate and mean maximal double product were not different when compared to an age-matched control group. Of the 48 patients who began the test with PE, in 23 (48%) it disappeared while PE persisted in 25 (52%). In 16 cases the disappearance of the PE was sudden and in seven it was progressive. Pre-excitation persisted in 39.5% of patients with type A and in 88.8% with type B (p less than 0.01). ST-segment depression was observed in 76.6% of patients with PE and in 28.6% of cases without PE (p less than 0.01). ST-segment depression occurred in 44.8% of patients with type A and in 100% of cases with type B (p less than 0.05). Transient abnormal Thallium-201 scans were observed in 62.5% of patients without PE and in 20% with PE. No patients showed exertional arrhythmias. This study suggests the possibility of measuring the duration of the refractory period of the accessory pathway in those patients n which the PE disappears suddenly, at a given heart rate.

  6. [Wolff-Parkinson-White syndrome. Value of intravenous flecainide for detecting Kent's pathways with short refractory period].

    PubMed

    Talard, P; Cointe, R; Bru, P; Moyal, C; Lacombe, P; Bremondy, M; Levy, S; Gerard, R

    1990-04-01

    The aim of this study was to assess the value of a non-invasive test in detecting accessory pathways with short anterograde effective refractory periods (AERP) (less than or equal to 270 ms) in patients with the Wolff-Parkinson-White syndrome. An intravenous injection of Flecainide acetate was administered to 19 consecutive patients referred for electrophysiological investigation of a WPW syndrome with permanent pre-excitation of the surface electrocardiogram. The first 8 patients (Group I) received a dose of 1.5 mg/kg over 5 minutes and the following 11 patients (Group II) were given 2 mg/kg in 5 minutes. In Group I, preexcitation disappeared in 3 patients (37.5%) who all had accessory pathways with AERP greater than 270 ms. It persisted in the other 5 patients (62.5%) of whom 4 had AERP less than or equal to 270 ms and 1 an AERP greater than 270 ms (false negative). In Group II, preexcitation disappeared in 8 patients (72.2%) of whom 4 had AERP greater than 270 ms and 4 had AERP less than 270 ms (false positives). Preexcitation persisted in the 3 other patients (27.3%); the AERP was less than or equal to 270 ms in 2 patients and greater than 270 ms in the other patients. These results suggest that intravenous Flecainide acetate at the dose of 1.5 mg/kg could be useful in differentiating WPW syndromes with long refractory periods (greater than 270 ms) from those with short refractory periods (less than or equal to 270 ms) with a satisfactory sensitivity and specificity, and that further studies on larger numbers of patients are required to confirm this hypothesis.

  7. [Ablation of accessory pathways by radiofrequency current. Towards a simplified approach of Wolff-Parkinson-White syndrome?].

    PubMed

    Atallah, G; Touboul, P; Zuloaga, C; Kirkorian, G; Lavaud, P; Moncada, E; Chevalier, P; Canu, G; Claudel, J P

    1993-06-01

    From December 1990 to April 1992, 41 consecutive patients (22 men and 19 women with an average age of 35 +/- 16 years -6-72) underwent ablation of accessory atrioventricular conduction pathways (Bundles of Kent) for poorly tolerated and/or medically resistant supraventricular tachycardias. In 33 cases, the arrhythmia was a paroxysmal SVT, in 7 cases atrial fibrillation, and in 1 patient incessant junctional tachycardia causing left ventricular dysfunction. The Wolff-Parkinson-White syndrome was apparent in 30 patients and concealed in 11 cases. The location of the Kent bundle was left lateral in 22 cases (53.7%), posterior paraseptal in 9 cases (21.9%), right lateral in 5 cases (12.2%) and anterior paraseptal in 5 cases (12.2%). The Kent bundles were ablated by radiofrequency currents in 38 cases (92.7%); in 2 patients (4.9%) in whom radiofrequency could not be used (increased impedance) high energy electrical shock was successful. In one patient (2.4%), it was not possible to suppress the Kent bundle. A single session of radiofrequency ablation was sufficient in 33 cases: 7 cases (17.5%) required 2 (4) or 3 (3) sessions. The average number of sites of application per patient was 8.8 +/- 8.8. The duration and intensity were respectively 32.2 +/- 9.3 (5-60) seconds and 25 +/- 15 (20-30) watts. With an average follow-up of tachycardia or of ventricular preexcitation have been observed in the 40 patients. In addition, in 36 patients, electrophysiological control studies confirmed the initial result with absence of any disturbance of nodohisian conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. [Surgery of Wolff-Parkinson-White: value of the epicardial approach. Apropos of 28 surgically treated cases].

    PubMed

    Menasché, P; Leclercq, J F; Cauchemez, B; Coumel, P; Slama, R; Piwnica, A

    1987-01-01

    The authors report their experience of 28 cases of the Wolff-Parkinson-White (WPW) syndrome treated by surgery. Four patients had multiple accessory pathways; of the 32 bundles of Kent detected, 16 were in the postero-septal region. Surgery, performed under cardio-pulmonary bypass after epicardial mapping, consisted in atrioventricular disconnection using no special physical agent. With the exception of 2 cases, the left lateral accessory pathways were operated using a classical left intraatrial approach whereas in the right lateral and septal forms the main procedure of dissection of the right atrioventricular groove was carried out by an epicardial approach. There was one operative death due to haemodynamic and haemorrhagic problems in a top class athlete with two bundles of Kent, the interruption of which required two consecutive bypass procedures. In the 27 survivors, 29 of the 30 accessory pathways were successfully interrupted (96 p. 100). The only failure occurred in a patient with two bundles of Kent. On the other hand, in 2 patients, complete atrioventricular block was successfully obtained by surgical section of the His bundle during the same procedure in one case, and by postoperative catheter ablation in the other case in which surgery had failed. There were no cases of accidental permanent atrioventricular block. The results in this series confirm the value of surgery in the treatment of the WPW syndrome, especially in the septal forms which are reputed to be the most difficult but in which the approach is greatly simplified by the initial dissection of the tricuspid ring by an epicardial approach.(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Phase mapping of radionuclide gated biventriculograms in patients with sustained ventricular tachycardia or Wolff-Parkinson-White syndrome

    SciTech Connect

    Le Guludec, D.; Bourguignon, M.; Sebag, C.; Valette, H.; Sirinelli, A.; Davy, J.M.; Syrota, A.; Motte, G.

    1987-01-01

    Accuracy of Fourier phase mapping of radionuclide gated biventriculograms in detecting the origin of abnormal ventricular activation was studied during ventricular tachycardia or preexcitation. Group I included six patients suffering from clinical recurrent VT; 3 gated blood pool studies were acquired for each patient: during sinus rhythm, right ventricular pacing, and induced sustained VT-Group II included seven patients with Wolff-Parkinson-White syndrome and recurrent paroxysmal tachycardia; 3 gated blood pool studies were acquired for each patient: during sinus rhythm, right atrial pacing and orthodromic reciprocating tachycardia. Each acquisition lasted 5 min, in 30 degrees-40 degrees left anterior oblique projection. In Group I, the Fourier phase mapping was consistent with QRS morphology and axis during VT (5/6), except in one patient with LV aneurysm and LBBB electrical pattern during VT. Origin of VT on phase mapping was located in the right ventricle (n = 2) or in left ventricle (n = 4), at the border of wall motion abnormalities each time they existed (5/6). In Group II, the phase advance correlated with the location of the accessory pathway determined by ECG and endocardial mapping (n = 6) and per-operative epicardial mapping (n = 1). Discrimination between anterior and posterior localization of paraseptal pathways and location of intermittent preexcitation was not possible. We conclude that Fourier phase mapping is an accurate method for locating the origin of VT and determining its etiology. It can help locate the site of ventricular preexcitation in patients with only one accessory pathway; its accuracy in locating multiple accessory pathways remains unknown.

  10. Photoinduced Acrylate Polymerization: Unexpected Reduction in Chain Branching.

    PubMed

    Wenn, Benjamin; Reekmans, Gunter; Adriaensens, Peter; Junkers, Thomas

    2015-08-01

    The branching stemming from midchain radical formation in n-butyl acrylate polymerization is investigated via melt-state (13) C NMR measurements. The dependence of the degree of branching (DB) on the monomer conversion of the system is examined for photoinduced polymerizations, revealing a steady increase in branching with conversion. For polymerization at moderate light intensities, an increase in branching from 0.03% to 0.37% is observed for polymerizations at 60 °C, which is fivefold below the level of branching observed in thermally initiated polymerizations under otherwise identical reaction conditions. The reason for this overall reduction in branching remains momentarily unclear; yet, a strong dependence of branching on light intensity is observed. While polymerization under a 1 W LED lamp results at almost full monomer conversion in branching degrees of 0.22%, polymerization under a 400 W lamp yields 1.81% of chain branches.

  11. Preparation of diarylethene copolymers and their photoinduced refractive index change

    NASA Astrophysics Data System (ADS)

    Cho, S. Y.; Yoo, M.; Shin, H.-W.; Ahn, K.-H.; Kim, Y.-R.; Kim, E.

    2003-01-01

    Diarylethene copolymers were synthesized from 1-(6 '-vinyl-2 '-methylbenzo[ b]thiophene-3 '-yl)-2-(2 ''-methylbenzo [ b]thiophene-3 ''-yl)hexafluorocyclopentene (VMBTF6) and 1-[6 '-(4 '''-vinylbenzoyl)-2 '-methylbenzo[ b]thiophene-3 '-yl]-2-(2 ''-methylbenzo[ b]thiophene-3 ''-yl)hexafluorocyclopentene (VBMBTF6) via living free radical techniques using stable TEMPO derivatives. The diarylethene content was controlled by the feed ratio of diarylethene derivatives and styrene. Transparent photochromic polymer films were prepared from the diarylethene copolymers with narrow molecular weight dispersion (PD˜1.3) by spin coating method. Photoinduced refractive index changes (Δ nTE) of the polymer films, with 25 mol% of diaryethene content, accompanied by the photochromic change were determined as 0.0009 and 0.0030 for poly(styrene- ran -VMBTF6) and poly(styrene- ran-VBMBTF6), respectively.

  12. Photoinduced charge transfer phase transition in cesium manganese hexacyanoferrate

    SciTech Connect

    Matsuda, Tomoyuki; Tokoro, Hiroko; Hashimoto, Kazuhito; Ohkoshi, Shin-ichi

    2007-05-01

    Cesium manganese hexacyanoferrate, Cs{sub 1.51}Mn[Fe(CN){sub 6}], shows a thermal phase transition between Mn{sup II}-NC-Fe{sup III} [high-temperature (HT) phase] and Mn{sup III}-NC-Fe{sup II} [low-temperature (LT) phase] with phase transition temperatures of 170 K (HT{yields}LT) and 230 K (LT{yields}HT). The LT phase shows ferromagnetism with Curie temperature of 7 K and coercive field of 60 Oe. Irradiating with 532 nm laser light converts the LT phase into the photoinduced (PI) phase, which does not have spontaneous magnetization. The electronic state of the PI phase corresponds to that of the HT phase and the relaxation temperature from the PI to the LT phase is observed at 90 K.

  13. Photoinduced surface voltage mapping study for large perovskite single crystals

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojing; Liu, Yucheng; Gao, Fei; Yang, Zhou; Liu, Shengzhong Frank

    2016-05-01

    Using a series of illumination sources, including white light (tungsten-halogen lamp), 445-nm, 532-nm, 635-nm, and 730-nm lasers, the surface photovoltage (SPV) images were mapped for centimeter-sized CH3NH3PbX3 (X = Cl, Br, I) perovskite single crystals using Kelvin probe force microscopy. The significant SPV signals were observed to be wavelength-dependent. We attribute the appreciable SPV to the built-in electric field in the space charge region. This study shines light into the understanding of photoinduced charge generation and separation processes at nanoscale to help advance the development of perovskite solar cells, optoelectronics, laser, photodetector, and light-emitting diode (LED).

  14. Photoinduced Magnetization in a Thin Fe-CN-Co Film.

    NASA Astrophysics Data System (ADS)

    Huh, Y. D.; Talham, D. R.; Park, J.-H.; Meisel, M. W.

    2004-03-01

    We have studied the photoinduced magnetization of a new low dimensional system, a thin film of a Prussian blue derivative, Rb_jCo_k[Fe(CN)_6]_l. This film was synthesized by the sequential depositions of Rb^+/Co^2+ and [Fe(CN)_6]^3- ions on the surface of a templated Fe-CN-Co monolayer. In this novel 2D system, high spin states of the Fe and Co spins interact antiferromagnetically and experience long range ordering below 20 K. The spins form domains that exhibit behavior consistent with a cluster spin-glass description. Upon illumination with light, the population of the high spin states increases, resulting in a rapid increase of the magnetization of the film and a modification of the cluster spin-glass properties.

  15. DNA Intercalated Psoralen Undergoes Efficient Photoinduced Electron Transfer.

    PubMed

    Fröbel, Sascha; Reiffers, Anna; Torres Ziegenbein, Christian; Gilch, Peter

    2015-04-02

    The interaction of psoralens with DNA has been used for therapeutic and research purposes for decades. Still the photoinduced behavior of psoralens in DNA has never been observed directly. Femtosecond transient absorption spectroscopy is used here to gain direct insight into the photophysics of a DNA-intercalated psoralen (4'-aminomethyl-4,5',8-trimethyl-psoralen (AMT)). Intercalation reduces the excited singlet lifetime of AMT to 4 ps compared with 1400 ps for AMT in water. This singlet quenching prohibits the population of the triplet state that is accessed in free AMT. Instead, a DNA to AMT electron transfer takes place. The resulting radical pair decays primarily via charge recombination with a time constant of 30 ps. The efficient electron transfer observed here reveals a completely new aspect of the psoralen-DNA interaction.

  16. Method for characterizing bulk recombination using photoinduced absorption

    NASA Astrophysics Data System (ADS)

    Wilson, Nora M.; Sandén, Simon; Sandberg, Oskar J.; Österbacka, Ronald

    2017-03-01

    The influence of reaction order and trap-assisted recombination on continuous-wave photoinduced absorption measurements is clarified through analytical calculations and numerical simulations. The results reveal the characteristic influence of different trap distributions and enable distinguishing between shallow exponential and Gaussian distributions and systems dominated by direct recombination by analyzing the temperature dependence of the in-phase and quadrature signals. The identifying features are the intensity dependence of the in-phase at high intensity, P A I ∝ I γ HI , and the frequency dependence of the quadrature at low frequency, P A Q ∝ ω γ LF . For direct recombination, γHI and γLF are temperature independent, and for an exponential distribution, they depend on the characteristic energy Ech as γ HI = 1 / ( 1 + E ch / k T ) and γ LF = k T / E ch , while a Gaussian distribution shows γHI and γLF as functions of I and ω, respectively.

  17. Photo-induced reflectivity in the mid and far infrared

    SciTech Connect

    Haar, P.; Harrington, K.J.; Schwettman, H.A.

    1995-12-31

    Interest in switching FEL beams has motivated studies of photo-induced reflectivity in the mid and far infrared. We are particularly interested in Ge{sup 4}, GaAs, and Si{sup 5}, materials that can be pumped with a visible or near-IR conventional laser and which together cover the wavelengths from 3-100{mu}m. We have made quantitative measurements to determine the induced reflectivity, carrier lifetime, and transient absorption of these materials at several wavelengths across this range using a variety of pump laser wavelengths and pulse lengths. These measurements allow us to determine the feasibility of single pulse selection and cavity dumping with our FELs at high repetition rates.

  18. Photoinduced electron transfer between benzyloxy dendrimer phthalocyanine and benzoquinone

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Ma, Dongdong; Pan, Sujuan; Wu, Shijun; Jiang, Yufeng; Zeng, Di; Yang, Hongqin; Peng, Yiru

    2016-10-01

    Photo-induced electron transfer (PET) is an important and fundamental process in natural photosynthesis. To mimic such interesting PET process, a suitable donor and acceptor couple were properly chosen. Dendrimer phthalocyanines and their derivatives have emerged as promising materials for artificial photosynthesis systems. In this paper, the electron transfer between the light harvest dendrimer phthalocyanine (donor) and the 1,4-benzoquinone (acceptor) was studied by UV/Vis and fluorescence spectroscopic methods. It was found that fluorescence of phthalocyanine was quenched by benzoquinone (BQ) via excited state electron transfer, from the phthalocyanine to the BQ upon excitation at 610 nm. The Stern-Volmer constant (KSV) of electron transfer was calculated. Our study suggests that this dendritic phthalocyanine is an effective new electron donor and transmission complex and could be used as a potential artificial photosynthesis system.

  19. Luminescence and photoinduced absorption in ytterbium-doped optical fibres

    SciTech Connect

    Rybaltovsky, A A; Aleshkina, S S; Likhachev, M E; Bubnov, M M; Umnikov, A A; Yashkov, M V; Gur'yanov, Aleksei N; Dianov, Evgenii M

    2011-12-31

    Photochemical reactions induced in the glass network of an ytterbium-doped fibre core by IR laser pumping and UV irradiation have been investigated by analysing absorption and luminescence spectra. We have performed comparative studies of the photoinduced absorption and luminescence spectra of fibre preforms differing in core glass composition: Al{sub 2}O{sub 3} : SiO{sub 2}, Al{sub 2}O{sub 3} : Yb{sub 2}O{sub 3} : SiO{sub 2}, and P{sub 2}O{sub 5} : Yb{sub 2}O{sub 3} : SiO{sub 2}. The UV absorption spectra of unirradiated preform core samples show strong bands peaking at 5.1 and 6.5 eV, whose excitation plays a key role in photoinduced colour centre generation in the glass network. 'Direct' UV excitation of the 5.1- and 6.5-eV absorption bands at 244 and 193 nm leads to the reduction of some of the Yb{sup 3+} ions to Yb{sup 2+}. The photodarkening of ytterbium-doped fibres by IR pumping is shown to result from oxygen hole centre generation. A phenomenological model is proposed for the IR-pumping-induced photodarkening of ytterbium-doped fibres. The model predicts that colour centre generation in the core glass network and the associated absorption in the visible range result from a cooperative effect involving simultaneous excitation of a cluster composed of several closely spaced Yb{sup 3+} ions.

  20. Human structural variation: mechanisms of chromosome rearrangements

    PubMed Central

    Weckselblatt, Brooke; Rudd, M. Katharine

    2015-01-01

    Chromosome structural variation (SV) is a normal part of variation in the human genome, but some classes of SV can cause neurodevelopmental disorders. Analysis of the DNA sequence at SV breakpoints can reveal mutational mechanisms and risk factors for chromosome rearrangement. Large-scale SV breakpoint studies have become possible recently owing to advances in next-generation sequencing (NGS) including whole-genome sequencing (WGS). These findings have shed light on complex forms of SV such as triplications, inverted duplications, insertional translocations, and chromothripsis. Sequence-level breakpoint data resolve SV structure and determine how genes are disrupted, fused, and/or misregulated by breakpoints. Recent improvements in breakpoint sequencing have also revealed non-allelic homologous recombination (NAHR) between paralogous long interspersed nuclear element (LINE) or human endogenous retrovirus (HERV) repeats as a cause of deletions, duplications, and translocations. This review covers the genomic organization of simple and complex constitutional SVs, as well as the molecular mechanisms of their formation. PMID:26209074

  1. Photoinduced properties of nanocrystalline TiO2-anatase coating on Ti-based bone implants.

    PubMed

    Lorenzetti, Martina; Biglino, Daniele; Novak, Saša; Kobe, Spomenka

    2014-04-01

    The paper reports on the photoinduced properties of hydrothermally treated (HT) titanium used for bone implants. The anatase coatings composed of 30-100nm anatase crystals exhibited high photocatalytic activity and good photo-induced wettability, reaching a superhydrophilic state, despite the larger crystal dimensions than the previously reported optimal ones. These properties are due to a suitable combination of surface texture, roughness, thickness, crystal morphology and particle size, which allowed the two independent photo-induced phenomena to occur simultaneously. The results on caffeine degradation by photocatalysis and the prolonged effect (up to two weeks) of photo-induced wettability in dark suggested a possible applicability of the HT anatase coatings as bacteria-repelling surfaces for body implants, in favor of a better osseointegration in vivo.

  2. Photo-induced transformations in 2,2':5',2''-terthiophene thin films on silver.

    PubMed

    Alaverdyan, Yury; Johansson, Patrik; Käll, Mikael

    2006-03-28

    We report on transient photo-induced structural changes of 2,2':5',2''-terthiophene (3T) adsorbed on silver nanoparticles. Surface-enhanced Raman scattering (SERS) data show that the film thickness predetermines the eventual course of these changes. In particular, for high molecular concentrations (thick adsorbate layers), illumination leads to a photoinduced polymerization of the 3T film. For thin layers ( approximately monolayer coverage), the photoinduced spectral evolution is qualitatively different. We interpret the latter process as a cleavage of the terthiophene molecule, resulting in isolated thiophene units. Calculations of excitation energies for 3T + 3Ag+ and 1T + Ag+ revealed visible transitions, while calculated Raman frequencies indicated 1T as a possible photoproduct. As no photoinduced transformations are observed for 3T in the solid or solution phases, it is likely that the processes reported here originate in surface-enhanced charge-transfer between the Ag-surface and the organic adsorbate.

  3. Contributions of the Instituto Nacional de Cardiología in the diagnosis and treatment of the Wolff-Parkinson - White syndrome.

    PubMed

    Iturralde-Torres, Pedro; Márquez, Manlio F

    2010-01-01

    Since the first description of the disease now known as Wolff-Parkinson-White syndrome, much knowledge has been gained through several experimental and clinical studies all over the world. The Instituto Nacional de Cardiología Ignacio Chávez in Mexico City has not been the exception. In this report, we describe the clinical, electrocardiographic and electrophysiologic contributions of past and present researchers at the Institute, as well as the experience in the diagnosis and treatment of the W-P-W syndrome at this Instituto Nacional de Cardiología Ignacio Chávez.

  4. [Correlation between the orientation of the data wave and the topography of pre-excitation in the Wolff-Parkinson-White syndrome].

    PubMed

    Frank, R; Fontaine, G; Guiraudon, G; Cabrol, C; Grosgogeat, Y; Facquet, J

    1977-05-01

    A comparison between the epicardial siting of the zone of pre-excitation of the ventricle in Wolff-Parkinson-White syndrome and the ECG has allowed us to distinguish 6 topographical types, according to the orientation of the delta wave in the horizontal plane, and especially in the frontal plane which is often ignored: right anterior, left lateral, right of left anterior paraseptal, and right or left posterior paraseptal. The association of a heart defect with ventricular hypertrophy, or the coexistence of several associated accessory pathways prevents such correlation and makes it imperative to carry out intracavitary investigation and epicardial mapping to localise the accessory pathway if surgery is contemplated.

  5. Clonal immunoglobulin gene rearrangement in the infarcted lymph node syndrome.

    PubMed

    Laszewski, M J; Belding, P J; Feddersen, R M; Lutz, C T; Goeken, J A; Kemp, J D; Dick, F R

    1991-07-01

    The authors report a case of complete lymph node infarction in which a specific etiology could not be determined by morphologic or immunophenotypic studies; however, clonal rearrangement of the immunoglobulin gene was demonstrated by Southern blot hybridization of DNA extracted from the necrotic tissue. A subsequent lymph node biopsy later was diagnosed as malignant lymphoma, using morphologic, immunophenotypic and genotypic criteria. Identical clonally rearranged bands were present in DNA from both the infarcted nodal and the subsequent tissue biopsies. In the setting of lymph node necrosis, gene rearrangement studies may provide diagnostic information concerning clonality, even if morphologic and immunophenotypic studies are indeterminate for a lymphoproliferative process.

  6. Irradiance and Temperature Dependence of Photo-Induced Orientation in Two Azobenzene-Based Polymers

    DTIC Science & Technology

    1998-06-23

    and Almeria Natansohn* Department of Chemistry, Queen’s University, Kingston, Ontario, K7L 3N6 Paul Rochon Department of Physics, Royal Military...1. IRRADIANCE AND TEMPERATURE DEPENDENCE OF PHOTO-INDUCED ORIENTATION IN TWO AZOBENZENE-BASED POLYMERS Dennis Hore and Almeria Natansohn...IRRADIANCE AND TEMPERATURE DEPENDENCE OF PHOTO-INDUCED ORIENTATION IN TWO AZOBENZENE-BASED POLYMERS Dennis Hore and Almeria Natansohn Department of

  7. Alternating photoinduced mass transport triggered by light polarization in azobenzene containing sol-gel films

    NASA Astrophysics Data System (ADS)

    Fabbri, F.; Lassailly, Y.; Lahlil, K.; Boilot, J. P.; Peretti, J.

    2010-02-01

    Combined shear-force and near-field optical microscopies are used for real-time monitoring of the formation of photoinduced surface relief gratings in photochromic thin films containing azobenzene derivatives. The correlated optical and topographical images provide evidence that the direction of the photoinduced matter migration is defined by the light polarization pattern and that, for a given light intensity pattern, modulating the polarization between two orthogonal states gives rise to alternating mass transport.

  8. Antiproton-hydrogen atom rearrangement-annihilation cross section

    SciTech Connect

    Morgan, D.L. Jr.

    1986-08-22

    For antiproton energies of several eV or less, annihilation in matter occurs through atomic rearrangement processes in which the antiproton becomes bound to a nucleus prior to annihilation. Existing calculations of the antiproton-hydrogen atom rearrangement cross section are semiclassical and employ the Born-Oppenheimer approximation. They also employ various arguments in regard to the behavior of the system when the Born-Oppenheimer approximation breaks down at small antiproton-proton separations. These arguments indicate that rearrangement is essentially irreversible. In the present study, a detailed investigation was made of the antiproton-hydrogen atom system when the Born-Oppenheimer approximation breaks down. The results of this study indicate that the previous arguments were approximately correct, but that there is a significant probability for rearrangement reversing prior to annihilation. This probability is estimated to be about 20%. 8 refs., 4 figs., 2 tabs.

  9. Somatic Rearrangement in B Cells: It's (Mostly) Nuclear Physics.

    PubMed

    Aiden, Erez Lieberman; Casellas, Rafael

    2015-08-13

    We discuss how principles of nuclear architecture drive typical gene rearrangements in B lymphocytes, whereas translocation hot spots and recurrent lesions reflect the extent of AID-mediated DNA damage and selection.

  10. The Petasis-Ferrier rearrangement: developments and applications.

    PubMed

    Minbiole, Emily C; Minbiole, Kevin P C

    2016-04-01

    In the mid-1990s, Petasis reexamined a promising but infrequently used rearrangement strategy, the so-called Ferrier-type-II reaction, and provided it with a modern update. Previously, Ferrier had developed a strategy where carbohydrate derivatives would undergo a fragmentation/aldol-type recombination sequence, generating a carbocycle, albeit under the promotion of stoichiometric mercury salts. Petasis' new variant showed the promise to effectively and stereoselectively convert a range of cyclic vinyl acetals to useful tetrahydrofurans and tetrahydropyrans, using less toxic promoters. Since these first reports, the 'Petasis-Ferrier rearrangement' has represented a vibrant area of research and innovation for organic chemists. With numerous applications in complex natural product total synthesis, the utility of the reaction has been resoundingly established. Recent developments have extended the reaction to a broader synthetic context, allowing for in situ generation of rearrangement substrates and more liberal interpretation of what fragmentation/recombination reactions warrant the designation of a Petasis-Ferrier rearrangement.

  11. Rearrangement and annihilation in antihydrogen-atom scattering

    SciTech Connect

    Jonsell, Svante

    2008-08-08

    I review some results for annihilation and rearrangement processes in low-energy antihydrogen-hydrogen and antihydrogen-helium scattering. For the strong nuclear force results using a {delta}-function potential are compared to a scattering length approach. It is found that the {delta}-function potential does not give correct annihilation cross sections in the case of antihydrogen-helium scattering. Problem associated with the use of the Born-Oppenheimer approximation for rearrangement calculations are reviewed.

  12. Ultrafast infrared studies of complex ligand rearrangements in solution

    SciTech Connect

    Payne, Christine K.

    2003-01-01

    The complete description of a chemical reaction in solution depends upon an understanding of the reactive molecule as well as its interactions with the surrounding solvent molecules. Using ultrafast infrared spectroscopy it is possible to observe both the solute-solvent interactions and the rearrangement steps which determine the overall course of a chemical reaction. The topics addressed in these studies focus on reaction mechanisms which require the rearrangement of complex ligands and the spectroscopic techniques necessary for the determination of these mechanisms. Ligand rearrangement is studied by considering two different reaction mechanisms for which the rearrangement of a complex ligand constitutes the most important step of the reaction. The first system concerns the rearrangement of a cyclopentadienyl ring as the response of an organometallic complex to a loss of electron density. This mechanism, commonly referred to as ''ring slip'', is frequently cited to explain reaction mechanisms. However, the ring slipped intermediate is too short-lived to be observed using conventional methods. Using a combination of ultrafast infrared spectroscopy and electronic structure calculations it has been shown that the intermediate exists, but does not form an eighteen-electron intermediate as suggested by traditional molecular orbital models. The second example examines the initial steps of alkyne polymerization. Group 6 (Cr, Mo, W) pentacarbonyl species are generated photolytically and used to catalyze the polymerization of unsaturated hydrocarbons through a series of coordination and rearrangement steps. Observing this reaction on the femto- to millisecond timescale indicates that the initial coordination of an alkyne solvent molecule to the metal center results in a stable intermediate that does not rearrange to form the polymer precursor. This suggests that polymerization requires the dissociation of additional carbonyl ligands before rearrangement can occur. Overall

  13. Competitive reaction pathways for o-anilide aryl radicals: 1,5- or 1,6-hydrogen transfer versus nucleophilic coupling reactions. A novel rearrangement to afford an amidyl radical.

    PubMed

    Rey, Valentina; Pierini, Adriana B; Peñéñory, Alicia B

    2009-02-06

    The photoinduced reactions of o-iodoanilides (o-IC6H4N(Me)COR, 4a-d) with sulfur nucleophiles such as thiourea anion (1, -SCNH(NH2)), thioacetate anion (2, MeCOS-), and sulfide anion (3, S(2-)) follow different reaction channels, giving the sulfides by a radical nucleophilic substitution or the dehalogenated products by hydrogen atom transfer pathways. After an initial photoinduced electron transfer (PET) from 1 to iodide 4, the o-amide aryl radicals 12 are generated. These aryl radicals 12 afford alternative reaction pathways depending on the structure of the alpha-carbonyl moiety: (a) 12b (R = Me) adds to 1 to render the methylthio-substituted compounds by quenching the thiolate anion intermediate with MeI after irradiation; (b) 12c (R = -CH2Ph) follows a 1,5-hydrogen transfer to give a stabilized alpha-carbonyl radical (17); and (c) 12d (R = t-Bu) affords 1,6-hydrogen transfer, followed by a 1,4-aryl migration to render an amidyl radical (20), which is reduced to the N-benzyl-N,2-dimethylpropanamide (10). Together with this last rearranged product, the ipso substitution derivative was also observed. Similar results were obtained in the PET reactions of 4d (R = t-Bu) with anions 2 and 3 under entrainment conditions with the enolate anion from cyclohexenone (5) or the tert-butoxide anion (6). From this novel rearrangement, and only under reductive conditions by PET reaction with anion 5, iodide 4d (R = t-Bu) affords quantitatively the propanamide 10. The energetic of the intramolecular rearrangements followed by radicals 12b-d were rationalized by B3LYP/6-31+G* calculations.

  14. Recurrent DNA inversion rearrangements in the human genome.

    PubMed

    Flores, Margarita; Morales, Lucía; Gonzaga-Jauregui, Claudia; Domínguez-Vidaña, Rocío; Zepeda, Cinthya; Yañez, Omar; Gutiérrez, María; Lemus, Tzitziki; Valle, David; Avila, Ma Carmen; Blanco, Daniel; Medina-Ruiz, Sofía; Meza, Karla; Ayala, Erandi; García, Delfino; Bustos, Patricia; González, Víctor; Girard, Lourdes; Tusie-Luna, Teresa; Dávila, Guillermo; Palacios, Rafael

    2007-04-10

    Several lines of evidence suggest that reiterated sequences in the human genome are targets for nonallelic homologous recombination (NAHR), which facilitates genomic rearrangements. We have used a PCR-based approach to identify breakpoint regions of rearranged structures in the human genome. In particular, we have identified intrachromosomal identical repeats that are located in reverse orientation, which may lead to chromosomal inversions. A bioinformatic workflow pathway to select appropriate regions for analysis was developed. Three such regions overlapping with known human genes, located on chromosomes 3, 15, and 19, were analyzed. The relative proportion of wild-type to rearranged structures was determined in DNA samples from blood obtained from different, unrelated individuals. The results obtained indicate that recurrent genomic rearrangements occur at relatively high frequency in somatic cells. Interestingly, the rearrangements studied were significantly more abundant in adults than in newborn individuals, suggesting that such DNA rearrangements might start to appear during embryogenesis or fetal life and continue to accumulate after birth. The relevance of our results in regard to human genomic variation is discussed.

  15. Evolution of atomic rearrangements in deformation in metallic glasses.

    PubMed

    Shang, B S; Li, M Z; Yao, Y G; Lu, Y J; Wang, W H

    2014-10-01

    Atomic rearrangements induced by shear stress are fundamental for understanding deformation mechanisms in metallic glasses (MGs). Using molecular dynamic simulation, the atomic rearrangements characterized by nonaffine displacements (NADs) and their spatial distribution and evolution with tensile stress in Cu50Zr50 MG were investigated. It was found that in the elastic regime the atomic rearrangements with the largest NADs are relatively homogeneous in space, but exhibit strong spatial correlation, become localized and inhomogeneous, and form large clusters as strain increases, which may facilitate the so-called shear transformation zones. Furthermore, initially they prefer to take place around Cu atoms which have more nonicosahedral configurations. As strain increases, the preference decays and disappears in the plastic regime. The atomic rearrangements with the smallest NADs are preferentially located around Cu atoms, too, but with more icosahedral or icosahedral-like atomic configurations. The preference is maintained in the whole deformation process. In contrast, the atomic rearrangements with moderate NADs distribute homogeneously, and do not show explicit preference or spatial correlation, acting as matrix during deformation. Among the atomic rearrangements with different NADs, those with largest and smallest NADs are nearest neighbors initially, but separating with increasing strain, while those with largest and moderate NADs always avoid to each other. The correlations in the fluctuations of the NADs confirm the long-range strain correlation and the scale-free characteristic of NADs in both elastic and plastic deformation, which suggests a universality of the scaling in the plastic flow in MGs.

  16. [Wolff-Parkinson-White syndrome. Correlation between the results of electrophysiological investigation and exercise tolerance testing on the electrical aspect of preexcitation].

    PubMed

    Lévy, S; Broustet, J P; Clémenty, J; Vircoulon, B; Guern, P; Bricaud, H

    1979-06-01

    Fourteen patients with permanent electrocardiographical features of the Wolff-Parkison-White syndrome in sinus rhythm referred for electrophysiological investigation also underwent maximal exercise tolerance tests. The working hypothesis was that in patients with the Wolff-Parkinson-White syndrome with accessory pathways of longer effective refractory periods than the normal pathway (group I) the delta wave should disappear on exercise, whilst in patients with accessory pathways with shorter refractory periods than the normal pathway (group II) the delta wave should persist. Of the 9 patients in group I,the delta wave regressed in 8 and persisted in 1 patient; of the 5 patients in group II, the delta wave persisted in 4 of them. Three patients had attacks of tachycardia during or just after the exercise tolerance test. These results suggest that the exercise tolerance test may help in the identification of patients with accessory pathways with long refractory periods, less susceptible to rapid ventricular rhythms should atrial fibrillation occur, and therefore with better prognoses.

  17. Fourth-order perturbative model for photoinduced internal conversion processes.

    PubMed

    Molesky, Brian P; Moran, Andrew M

    2013-12-27

    Essential to the functionality of numerous biological and synthetic molecular systems is the ability to rapidly convert electronic excitation energy into heat. Such internal conversion (IC) transitions often cannot be described by traditional second-order kinetic theories because of time-coincident electronic and nuclear relaxation processes. Here, we present a perturbative fourth-order phenomenological model for photoinduced IC that incorporates effects associated with finite laser bandwidths and nonequilibrium nuclear motions. Specialized knowledge of first-principles computational methods is not required, and many parameters can be obtained with standard spectroscopic measurements. The model is applied to the IC processes that precede electrocyclic ring-opening in α-terpinene. It is shown that the primary factor governing the shape of the population decay profile (Gaussian versus exponential) is the rate at which the wavepacket approaches the geometry corresponding to degeneracy between the excited states. Other parameters such as the displacement in the promoting mode and the thermal fluctuation amplitudes affect the sensitivity of the IC dynamics to motion of the wavepacket but do not alter the basic physical picture. Finally, we suggest a wavepacket representation of the IC process to visualize correlations between population-transfer dynamics and the amount of energy transferred from the system to the bath.

  18. Photo-induced chemical reaction of trans-resveratrol.

    PubMed

    Zhao, Yue; Shi, Meng; Ye, Jian-Hui; Zheng, Xin-Qiang; Lu, Jian-Liang; Liang, Yue-Rong

    2015-03-15

    Photo-induced chemical reaction of trans-resveratrol has been studied. UV B, liquid state and sufficient exposure time are essential conditions to the photochemical change of trans-resveratrol. Three principal compounds, cis-resveratrol, 2,4,6-phenanthrenetriol and 2-(4-hydroxyphenyl)-5,6-benzofurandione, were successively generated in the reaction solution of trans-resveratrol (0.25 mM, 100% ethanol) under 100 μW cm(-2) UV B radiation for 4h. cis-Resveratrol, originated from isomerization of trans-resveratrol, resulted in 2,4,6-phenanthrenetriol through photocyclisation reaction meanwhile loss of 2 H. 2,4,6-Phenanthrenetriol played a role of photosensitizer producing singlet oxygen in the reaction pathway. The singlet oxygen triggered [4+2] cycloaddition reaction of trans-resveratrol, and then resulted in the generation of 2-(4-hydroxyphenyl)-5,6-benzofurandione through photorearrangement and oxidation reaction. The singlet oxygen reaction was closely related to the substrate concentration of trans-resveratrol in solution.

  19. Ultrafast investigation of photoinduced charge transfer in aminoanthraquinone pharmaceutical product

    NASA Astrophysics Data System (ADS)

    Zhang, Song; Sun, Simei; Zhou, Miaomiao; Wang, Lian; Zhang, Bing

    2017-02-01

    We investigated the mechanism of intramolecular charge transfer and the following radiationless dynamics of the excited states of 1-aminoanthraquinone using steady state and time-resolved absorption spectroscopy combined with quantum chemical calculations. Following photoexcitation with 460 nm, conformational relaxation via twisting of the amino group, charge transfer and the intersystem crossing (ISC) processes have been established to be the major relaxation pathways responsible for the ultrafast nonradiative of the excited S1 state. Intramolecular proton transfer, which could be induced by intramolecular hydrogen bonding is inspected and excluded. Time-dependent density functional theory (TDDFT) calculations reveal the change of the dipole moments of the S0 and S1 states along the twisted coordinate of the amino group, indicating the mechanism of twisted intra-molecular charge transfer (TICT). The timescale of TICT is measured to be 5 ps due to the conformational relaxation and a barrier on the S1 potential surface. The ISC from the S1 state to the triplet manifold is a main deactivation pathway with the decay time of 28 ps. Our results observed here have yield a physically intuitive and complete picture of the photoinduced charge transfer and radiationless dynamics in anthraquinone pharmaceutial products.

  20. Photoinduced Bimolecular Electron Transfer from Cyano Anions in Ionic Liquids.

    PubMed

    Wu, Boning; Liang, Min; Maroncelli, Mark; Castner, Edward W

    2015-11-19

    Ionic liquids with electron-donating anions are used to investigate rates and mechanisms of photoinduced bimolecular electron transfer to the photoexcited acceptor 9,10-dicyanoanthracene (9,10-DCNA). The set of five cyano anion ILs studied comprises the 1-ethyl-3-methylimidazolium cation paired with each of these five anions: selenocyanate, thiocyanate, dicyanamide, tricyanomethanide, and tetracyanoborate. Measurements with these anions dilute in acetonitrile and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide show that the selenocyanate and tricyanomethanide anions are strong quenchers of the 9,10-DCNA fluorescence, thiocyanate is a moderately strong quencher, dicyanamide is a weak quencher, and no quenching is observed for tetracyanoborate. Quenching rates are obtained from both time-resolved fluorescence transients and time-integrated spectra. Application of a Smoluchowski diffusion-and-reaction model showed that the complex kinetics observed can be fit using only two adjustable parameters, D and V0, where D is the relative diffusion coefficient between donor and acceptor and V0 is the value of the electronic coupling at donor-acceptor contact.

  1. Origin of photo-induced transmitting oscillations in chalcogenide glasses.

    PubMed

    Tao, HaiZheng; Yang, ZhiYong; Lucas, Pierre

    2009-09-28

    Light-induced oscillatory behaviors of transmission in chalcogenide glasses are investigated using a continuous wave tunable Ti-sapphire laser. It is shown that phase change, thermal fluctuation, nonlinear index change and periodic self focusing are not at the origin of light-induced oscillatory transmittance in chalcogenide glasses. Instead, results indicate that the interference of transmitting and reflecting light is at the origin of the oscillatory behaviors of transmitted light. Just like the principle of Fabry-Pérot interferometer, these interferences result in a periodic change in transmission as the related interferential beams get in and out of phase. However, this transmitting oscillatory behavior can be registered by the detector only when the change of optical path length difference initiated by photo-induced effects is slower enough compared with the corresponding response time of the detector. Several photo-structural effects contribute to that phenomenon including photo-expansion, photo-darkening, and permanent self focusing. It appears that fluctuations of the light source intensity induce a wide distribution of the oscillatory periods.

  2. Diel variations in photoinduced oxidation of Hg0 in freshwater.

    PubMed

    Garcia, Edenise; Poulain, Alexandre J; Amyot, Marc; Ariya, Parisa A

    2005-05-01

    Experiments have been conducted to determine diel variations in photoinduced Hg0 oxidation in lake water under natural Hg0(aq) concentrations. Pseudo-first-order rates of photooxidation (k') were calculated for water freshly collected in a Canadian Shield lake, Lake Croche (45 degrees 56' N, 74 degrees 00' W), at different periods of the day and subsequently incubated in the dark. Hg0 oxidation rates ranged from 0.02 to 0.07 h(-1), increasing from sunrise to noon and then decreasing throughout the remainder of the day. These changes paralleled those in sunlight intensity integrated over 1 h preceding water collection, and suggested that the water freshly collected in daylight was rich in photochemically produced Hg0 oxidants. It was also estimated that under intense solar radiation, even if oxidation rates reached a peak, reduction of Hg(II) was the prevalent redox process. Inversely, Hg0 oxidation overcame DGM production during the night or at periods of weaker light intensity. Overall, these findings explain the decreases in the DGM pool generally observed overnight. They also support previous reports that, during summer days, volatilization of Hg0 from water represent an important step in the Hg cycle in freshwater systems.

  3. Photoinduced isomerization of lycopene and application to tomato cultivation.

    PubMed

    Heymann, Thomas; Raeke, Julia; Glomb, Marcus A

    2013-11-20

    The present study aimed to investigate if growth conditions have an impact on the isomeric composition of lycopene in tomatoes. First a model system for photoinduced isomerization was established. Tomato extracts were irradiated with a halogen lamp, whose wavelength spectrum is close to the spectrum of daylight and thus mimics field-grown cultivation. Different optical filters were interposed between lamp and samples to simulate greenhouse conditions. 5-cis-Lycopene was formed preferentially while the concentration of 7-cis-lycopene decreased in field-grown model systems. The change of isomerization in greenhouse model systems led to a significantly different ratio. Consequently 5-cis- and 7-cis-lycopene were identified as potent markers for the differentiation of various lighting conditions during cultivation. This result was verified in biological samples. Authentic field-grown tomatoes (var. Lycopersicon esculentum Mill. var. commune L. H. Bailey "Harzfeuer") showed a significantly higher content of 5-cis-lycopene 5.90 ± 0.45% compared to tomatoes of the same variety grown under electric lighting 4.11 ± 0.10%. Additionally, the ratio of 7-cis-lycopene was significantly lower under field-grown conditions.

  4. Theoretical approach to photoinduced inhomogeneous anisotropy in bacteriorhodopsin films.

    PubMed

    Acebal, P; Carretero, L; Blaya, S; Murciano, A; Fimia, A

    2007-07-01

    The aim of this work was to perform a complete study of the dynamic and steady-state photoinduced processes of thick bacteriorhodopsin (bR) films, taking into account all the physical parameters and the coupling of rate equations with the energy transfer equation. The theoretical approach was compared with experimental data, and good concordance was found between both sets of data. The theoretical approach shows that the values of the rate constants for solid bR films are about two or three orders of magnitude lower than those observed in solution. It can also be noted that the temperature change during the experiment had a great influence on the final values of transmittance and, consequently, on the inhomogeneous distribution along the coordinate of light propagation. The study shows that, depending on the intensity and wavelength of the pump beam, we can obtain a very inhomogeneous profile of the population densities, which implies an inhomogeneous profile of the birefringence and dichroism. Therefore, this must be taken into account in the applications described for this system.

  5. Electric Field Dependence of Photo-Induced Field Emission Current.

    NASA Astrophysics Data System (ADS)

    Egert, Charles Michael

    We have measured the photo-induced field emission current from a tungsten field emitter as a function of electric field. These experiments were performed with a retardation energy analyzer to measure total current and a 127(DEGREES) cylindrical differential energy analyzer to measure the energy resolved PFE current. The results of these experiments are compared with a simple theory of PFE, developed by Schwartz and Schaich, which is an extension of field emission theory including the surface photoeffect, but assuming constant photoexcitation matrix elements. Our experimental results disagree with this theory in two ways: First, for high fields and photon energy (electrons emitted above the field emission barrier maximum) theory predicts a larger increase in PFE current than is observed experimentally. Second, we have also confirmed the existence of a field dependent oscillatory component of the PFE current emitted from the W(110) surface with photon energies of 2.7 eV and 3.5 eV. The simple theory described here, as well as more sophisticated calculations, have been unable to explain this oscillatory feature. We have also reported, for the first time, the field dependence of the energy resolved PFE current measured with a 127(DEGREES) cylindrical energy analyzer. These preliminary results show evidence of the oscillatory component previously only observed in the total PFE current.

  6. Photoinduced Giant Dielectric Constant in Lead Halide Perovskite Solar Cells.

    PubMed

    Juarez-Perez, Emilio J; Sanchez, Rafael S; Badia, Laura; Garcia-Belmonte, Germá; Kang, Yong Soo; Mora-Sero, Ivan; Bisquert, Juan

    2014-07-03

    Organic-inorganic lead trihalide perovskites have emerged as an outstanding photovoltaic material that demonstrated a high 17.9% conversion efficiency of sunlight to electricity in a short time. We have found a giant dielectric constant (GDC) phenomenon in these materials consisting on a low frequency dielectric constant in the dark of the order of ε0 = 1000. We also found an unprecedented behavior in which ε0 further increases under illumination or by charge injection at applied bias. We observe that ε0 increases nearly linearly with the illumination intensity up to an additional factor 1000 under 1 sun. Measurement of a variety of samples of different morphologies, compositions, and different types of contacts shows that the GDC is an intrinsic property of MAPbX3 (MA = CH3NH3(+)). We hypothesize that the large dielectric response is induced by structural fluctuations. Photoinduced carriers modify the local unit cell equilibrium and change the polarizability, assisted by the freedom of rotation of MA. The study opens a way for the understanding of a key aspect of the photovoltaic operation of high efficiency perovskite solar cells.

  7. Ultrafast investigation of photoinduced charge transfer in aminoanthraquinone pharmaceutical product

    PubMed Central

    Zhang, Song; Sun, Simei; Zhou, Miaomiao; Wang, Lian; Zhang, Bing

    2017-01-01

    We investigated the mechanism of intramolecular charge transfer and the following radiationless dynamics of the excited states of 1-aminoanthraquinone using steady state and time-resolved absorption spectroscopy combined with quantum chemical calculations. Following photoexcitation with 460 nm, conformational relaxation via twisting of the amino group, charge transfer and the intersystem crossing (ISC) processes have been established to be the major relaxation pathways responsible for the ultrafast nonradiative of the excited S1 state. Intramolecular proton transfer, which could be induced by intramolecular hydrogen bonding is inspected and excluded. Time-dependent density functional theory (TDDFT) calculations reveal the change of the dipole moments of the S0 and S1 states along the twisted coordinate of the amino group, indicating the mechanism of twisted intra-molecular charge transfer (TICT). The timescale of TICT is measured to be 5 ps due to the conformational relaxation and a barrier on the S1 potential surface. The ISC from the S1 state to the triplet manifold is a main deactivation pathway with the decay time of 28 ps. Our results observed here have yield a physically intuitive and complete picture of the photoinduced charge transfer and radiationless dynamics in anthraquinone pharmaceutial products. PMID:28233835

  8. Highly Twisted Triarylamines for Photoinduced Intramoleculer ChargeTransfer

    SciTech Connect

    Chudomel, J. M.; Yang, B. Q.; Barnes, M. D.; Achermann, M.; Mague, J. T.; Lahti, P. M.

    2011-08-04

    9-(N,N-Dianisylamino)anthracene (9DAAA), 9-(N,N-dianisylamino)dinaphth([1,2-a:2'-1'-j]-anthracene (9DAAH), and 9,10-bis(N,N-dianisylamino)anthracene (910BAA) were synthesized as highly twisted triarylamines with potential for photoexcited internal charge transfer. Crystallography of 9DAAA shows its dianisylamino group to be twisted nearly perpendicular to its anthracene unit, similar to a report for 910BAA. The solution fluorescence spectra show strong bathochromic shifts for each of the three molecular systems with strongly decreased quantum efficiency in higher polarity solvents. Solution-phase (ensemble) time-resolved photoluminescence measurements show up to 4-fold decreases in fluorescence lifetime in acetonitrile compared to hexane. The combined results are consistent with photoinduced, transient intramolecular charge-transfer from the bis-anisylamine unit to the polycyclic aromatic unit. Computational modeling is in accord with intramolecular transfer of electron density from the bis-anisylamino unit to the anthracene, based on in comparisons of HOMO and LUMO.

  9. Photoinduced superhydrophilicity: a kinetic study of time dependent photoinduced contact angle changes on TiO2 surfaces.

    PubMed

    Foran, Philip S; Boxall, Colin; Denison, Kieth R

    2012-12-21

    Transparent TiO(2) thin films were prepared on quartz substrates via a reverse micelle, sol-gel, spin-coating technique. The time dependence of the TiO(2) film photoinduced superhydrophilicity (PISH) was measured by goniometric observation of the contact angle, θ, of sessile water drops at the film surfaces. In these measurements, the TiO(2) substrate was illuminated by 315 nm light and drops were sequentially applied at a range of illumination times. Using a model for the wetting of heterogeneous surfaces derived by Israelachvili and Gee, these measurements were used to calculate the time dependence of f(2), the fractional surface coverage of the TiO(2) surface by adventitious contaminating organics (Israelachvili, J. N.; Gee, M. L. Contact angles on chemically heterogeneous surfaces. Langmuir 1989, 5, 288). Extending this model to include a Langmuir-Hinshelwood based kinetic analysis of f(2) as a function of time allowed for calculation of an expected value for θ immediately prior to illumination, that is, at illumination time t = 0. Such expected values of θ at t = 0 were calculated using two possible values of θ(1), the contact angle on a pristine unilluminated homogeneous TiO(2) surface: (i) θ(1) = 4° as suggested by, inter alia, Zubkov et al. (Zubkov, T.; Stahl, D.; Thompson, T. L.; Panayotov, D.; Diwald, O.; Yates, J. T. Ultraviolet Light-Induced Hydrophilicity Effect on TiO(2)(110)(1 × 1). Dominant Role of the Photooxidation of Adsorbed Hydrocarbons Causing Wetting by Water Droplets. J. Phys. Chem. B2005, 109, 15454); and (ii) where θ(1) = 25°, as suggested by Fujishima et al., representative of a more hydrophobic homogeneous TiO(2) surface that reconstructs upon exposure to ultraband gap illumination into a hydrophilic surface where θ(1) → 0° (Fujishima, A.; Zhang, X.; Tryk, D. A. TiO(2) photocatalysis and related surface phenomena Surf. Sci. Rep.2008, 63, 515). Analysis of data from our experiments and from selected literature sources

  10. Retardation of the orientation relaxation of azo-dye doped amorphous polymers upon photoinduced isomerization

    NASA Astrophysics Data System (ADS)

    Chan, S. W.; Quatela, A.; Casalboni, M.; Nunzi, J.-M.

    2006-08-01

    The orientation relaxation upon photo-induced isomerization of azo-dyes was studied. All-optical poling (AOP) and photo-induced birefringence, which are based on the mechanism of angular selective photo-isomerization, were employed to manipulate the angular distribution of azo-dyes (Disperse-red 1) doped in three different amorphous polymers: (poly(methyl methacrylate) PMMA, poly(carbonate) PC and poly(sulfone) PSU), with different glass transition temperature (T g). In the case of AOP, quasi-permanent macroscopic second-order nonlinear optical susceptibility χ (2) was inscribed in the dye-doped centro-symmetric polymer systems, while in the case of photo-induced birefringence, quasi-permanent birefringence Δn was inscribed in the dye-doped isotropic polymer systems. Relaxation of χ (2) and Δn were monitored upon different duration of AOP and photo-induced birefringence preparation. Experimental results show that azo-dye orientation relaxation follows the duration of the photo-nduced isomerization process: the longer the photo-induced isomerization process, the slower the relaxation of the inscribed χ (2) and Δn. In addition, retardation of the orientation relaxation does not follow a simple relation with hardness (T g) of the polymer host. Causes of the orientation relaxation retardation are discussed.

  11. QSARs for photo-induced toxicity of polycyclic aromatic hydrocarbons (PAHs)

    SciTech Connect

    Mekenyan, O.; Call, D.; Ankley, G.; Veith, G.

    1994-12-31

    Photo-induced toxicity of polycyclic aromatic hydrocarbons (PAHs) was found to be a result of competing internal and external factors which interact to produce a complex, multilinear relationship between toxicity and chemical structure. The relationship between molecular electronic structure and photo-dynamic effects was studied in both ground and excited states. A measure of the energy required for an electron to be elevated from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), or HOMO-LUMO gap, provided a useful ground state index to explain the persistence, light absorption, and eventual photo-induced toxicity of PAHs to Daphnia magna. The derived QSARs clearly distinguished photo-induced toxicity differences between pairs of structurally similar PAHs, such as phenanthrene and anthracene, benzo[a]anthracene and tetracene, etc. Those PAHs exhibiting photo-induced toxicity were consistently within a specific HOMO-LUMO gap range. The relationship between the excited state electronic parameters and toxicity was also studied. Significant correlations were found with the measured energies of singlet and triplet states from spectroscopic data. An investigation of the effect of substituent additions on photo-induced acute toxicity of parent PAHs revealed that alkyl and hydroxy moieties did not significantly reduce the HOMO-LUMO gap of the parent PAHs. Nitro, alkene and chloro substituents cause gap reductions, whereby certain derivatives of parent chemicals that were close to the ``toxic region`` of the electronic gap could become phototoxic with such additions.

  12. Gold-Catalyzed Rearrangements and Beyond

    PubMed Central

    2013-01-01

    Cycloisomerizations of enynes are probably the most representative carbon–carbon bond forming reactions catalyzed by electrophilic metal complexes. These transformations are synthetically useful because chemists can use them to build complex architectures under mild conditions from readily assembled starting materials. However, these transformations can have complex mechanisms. In general, gold(I) activates alkynes in the presence of any other unsaturated functional group by forming an (η2-alkyne)–gold complex. This species reacts readily with nucleophiles, including electron-rich alkenes. In this case, the reaction forms cyclopropyl gold(I) carbene-like intermediates. These can come from different pathways depending on the substitution pattern of the alkyne and the alkene. In the absence of external nucleophiles, 1,n-enynes can form products of skeletal rearrangement in fully intramolecular reactions, which are mechanistically very different from metathesis reactions initiated by the [2 + 2] cycloaddition of a Grubbs-type carbene or other related metal carbenes. In this Account, we discuss how cycloisomerization and addition reactions of substituted enynes, as well as intermolecular reactions between alkynes and alkenes, are best interpreted as proceeding through discrete cationic intermediates in which gold(I) plays a significant role in the stabilization of the positive charge. The most important intermediates are highly delocalized cationic species that some chemists describe as cyclopropyl gold(I) carbenes or gold(I)-stabilized cyclopropylmethyl/cyclobutyl/homoallyl carbocations. However, we prefer the cyclopropyl gold(I) carbene formulation for its simplicity and mnemonic value, highlighting the tendency of these intermediates to undergo cyclopropanation reactions with alkenes. We can add a variety of hetero- and carbonucleophiles to the enynes in the presence of gold(I) in intra- or intermolecular reactions, leading to the corresponding adducts with

  13. A comprehensive molecular cytogenetic analysis of chromosome rearrangements in gibbons

    PubMed Central

    Capozzi, Oronzo; Carbone, Lucia; Stanyon, Roscoe R.; Marra, Annamaria; Yang, Fengtang; Whelan, Christopher W.; de Jong, Pieter J.; Rocchi, Mariano; Archidiacono, Nicoletta

    2012-01-01

    Chromosome rearrangements in small apes are up to 20 times more frequent than in most mammals. Because of their complexity, the full extent of chromosome evolution in these hominoids is not yet fully documented. However, previous work with array painting, BAC-FISH, and selective sequencing in two of the four karyomorphs has shown that high-resolution methods can precisely define chromosome breakpoints and map the complex flow of evolutionary chromosome rearrangements. Here we use these tools to precisely define the rearrangements that have occurred in the remaining two karyomorphs, genera Symphalangus (2n = 50) and Hoolock (2n = 38). This research provides the most comprehensive insight into the evolutionary origins of chromosome rearrangements involved in transforming small apes genome. Bioinformatics analyses of the human–gibbon synteny breakpoints revealed association with transposable elements and segmental duplications, providing some insight into the mechanisms that might have promoted rearrangements in small apes. In the near future, the comparison of gibbon genome sequences will provide novel insights to test hypotheses concerning the mechanisms of chromosome evolution. The precise definition of synteny block boundaries and orientation, chromosomal fusions, and centromere repositioning events presented here will facilitate genome sequence assembly for these close relatives of humans. PMID:22892276

  14. Modeling of the primary rearrangement stage of liquid phase sintering

    NASA Astrophysics Data System (ADS)

    Malik Tahir, Abdul; Malik, Amer; Amberg, Gustav

    2016-10-01

    The dimensional variations during the rearrangement stage of liquid phase sintering could have a detrimental effect on the dimensional tolerances of the sintered product. A numerical approach to model the liquid phase penetration into interparticle boundaries and the accompanied dimensional variations during the primary rearrangement stage of liquid phase sintering is presented. The coupled system of the Cahn-Hilliard and the Navier-Stokes equations is used to model the penetration of the liquid phase, whereas the rearrangement of the solid particles due to capillary forces is modeled using the equilibrium equation for a linear elastic material. The simulations are performed using realistic physical properties of the phases involved and the effect of green density, wettability and amount of liquid phase is also incorporated in the model. In the first step, the kinetics of the liquid phase penetration and the rearrangement of solid particles connected by a liquid bridge is modeled. The predicted and the calculated (analytical) results are compared in order to validate the numerical model. The numerical model is then extended to simulate the dimensional changes during primary rearrangement stage and a qualitative match with the published experimental data is achieved.

  15. Induced dicentric chromosome formation promotes genomic rearrangements and tumorigenesis.

    PubMed

    Gascoigne, Karen E; Cheeseman, Iain M

    2013-07-01

    Chromosomal rearrangements can radically alter gene products and their function, driving tumor formation or progression. However, the molecular origins and evolution of such rearrangements are varied and poorly understood, with cancer cells often containing multiple, complex rearrangements. One mechanism that can lead to genomic rearrangements is the formation of a "dicentric" chromosome containing two functional centromeres. Indeed, such dicentric chromosomes have been observed in cancer cells. Here, we tested the ability of a single dicentric chromosome to contribute to genomic instability and neoplastic conversion in vertebrate cells. We developed a system to transiently and reversibly induce dicentric chromosome formation on a single chromosome with high temporal control. We find that induced dicentric chromosomes are frequently damaged and mis-segregated during mitosis, and that this leads to extensive chromosomal rearrangements including translocations with other chromosomes. Populations of pre-neoplastic cells in which a single dicentric chromosome is induced acquire extensive genomic instability and display hallmarks of cellular transformation including anchorage-independent growth in soft agar. Our results suggest that a single dicentric chromosome could contribute to tumor initiation.

  16. Chromosomal rearrangement interferes with meiotic X chromosome inactivation.

    PubMed

    Homolka, David; Ivanek, Robert; Capkova, Jana; Jansa, Petr; Forejt, Jiri

    2007-10-01

    Heterozygosity for certain mouse and human chromosomal rearrangements is characterized by the incomplete meiotic synapsis of rearranged chromosomes, by their colocalization with the XY body in primary spermatocytes, and by male-limited sterility. Previously, we argued that such X-autosomal associations could interfere with meiotic sex chromosome inactivation. Recently, supporting evidence has reported modifications of histones in rearranged chromosomes by a process called the meiotic silencing of unsynapsed chromatin (MSUC). Here, we report on the transcriptional down-regulation of genes within the unsynapsed region of the rearranged mouse chromosome 17, and on the subsequent disturbance of X chromosome inactivation. The partial transcriptional suppression of genes in the unsynapsed chromatin was most prominent prior to the mid-pachytene stage of primary spermatocytes. Later, during the mid-late pachytene, the rearranged autosomes colocalized with the XY body, and the X chromosome failed to undergo proper transcriptional silencing. Our findings provide direct evidence on the MSUC acting at the mRNA level, and implicate that autosomal asynapsis in meiosis may cause male sterility by interfering with meiotic sex chromosome inactivation.

  17. DNA Oligonucleotide Fragment Ion Rearrangements Upon Collision-Induced Dissociation

    NASA Astrophysics Data System (ADS)

    Harper, Brett; Neumann, Elizabeth K.; Solouki, Touradj

    2015-08-01

    Collision-induced dissociation (CID) of m/z-isolated w type fragment ions and an intact 5' phosphorylated DNA oligonucleotide generated rearranged product ions. Of the 21 studied w ions of various nucleotide sequences, fragment ion sizes, and charge states, 18 (~86%) generated rearranged product ions upon CID in a Synapt G2-S HDMS (Waters Corporation, Manchester, England, UK) ion mobility-mass spectrometer. Mass spectrometry (MS), ion mobility spectrometry (IMS), and theoretical modeling data suggest that purine bases can attack the free 5' phosphate group in w type ions and 5' phosphorylated DNA to generate sequence permuted [phosphopurine]- fragment ions. We propose and discuss a potential mechanism for generation of rearranged [phosphopurine]- and complementary y-B type product ions.

  18. Rearrangement and Grouping of Data Bits for Efficient Lossless Encoding

    NASA Astrophysics Data System (ADS)

    B, Ajitha Shenoy K.; Ajith, Meghana; Mantoor, Vinayak M.

    2017-01-01

    This paper describes the efficacy of rearranging and grouping of data bits. Lossless encoding techniques like Huffman Coding, Arithmetic Coding etc., works well on data which contains redundant information. The idea behind these techniques is to encode more frequently occurring symbols with less number of bits and more seldom occurring symbols with more number of bits. Most of the methods fail if there is a non-redundant data. We propose a method to re arrange and group data bits there by making the data redundant and then different lossless encoding techniques can be applied. In this paper we propose three different methods to rearrange the data bits, and efficient way of grouping them. This is first such attempt. We also justify the need of rearranging and grouping data bits for efficient lossless encoding.

  19. Conditions for predicting quasistationary states by rearrangement formula.

    PubMed

    Yamaguchi, Yoshiyuki Y; Ogawa, Shun

    2015-10-01

    Predicting the long-lasting quasistationary state for a given initial state is one of central issues in Hamiltonian systems having long-range interaction. A recently proposed method is based on the Vlasov description and uniformly redistributes the initial distribution along contours of the asymptotic effective Hamiltonian, which is defined by the obtained quasistationary state and is determined self-consistently. The method, to which we refer as the rearrangement formula, was suggested to give precise prediction under limited situations. Restricting initial states consisting of a spatially homogeneous part and small perturbation, we numerically reveal two conditions that the rearrangement formula prefers: One is a no Landau damping condition for the unperturbed homogeneous part, and the other comes from the Casimir invariants. Mechanisms of these conditions are discussed. Clarifying these conditions, we validate to use the rearrangement formula as the response theory for an external field, and we shed light on improving the theory as a nonequilibrium statistical mechanics.

  20. Conditions for predicting quasistationary states by rearrangement formula

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yoshiyuki Y.; Ogawa, Shun

    2015-10-01

    Predicting the long-lasting quasistationary state for a given initial state is one of central issues in Hamiltonian systems having long-range interaction. A recently proposed method is based on the Vlasov description and uniformly redistributes the initial distribution along contours of the asymptotic effective Hamiltonian, which is defined by the obtained quasistationary state and is determined self-consistently. The method, to which we refer as the rearrangement formula, was suggested to give precise prediction under limited situations. Restricting initial states consisting of a spatially homogeneous part and small perturbation, we numerically reveal two conditions that the rearrangement formula prefers: One is a no Landau damping condition for the unperturbed homogeneous part, and the other comes from the Casimir invariants. Mechanisms of these conditions are discussed. Clarifying these conditions, we validate to use the rearrangement formula as the response theory for an external field, and we shed light on improving the theory as a nonequilibrium statistical mechanics.

  1. Cell Division Drives Epithelial Cell Rearrangements during Gastrulation in Chick.

    PubMed

    Firmino, Joao; Rocancourt, Didier; Saadaoui, Mehdi; Moreau, Chloe; Gros, Jerome

    2016-02-08

    During early embryonic development, cells are organized as cohesive epithelial sheets that are continuously growing and remodeled without losing their integrity, giving rise to a wide array of tissue shapes. Here, using live imaging in chick embryo, we investigate how epithelial cells rearrange during gastrulation. We find that cell division is a major rearrangement driver that powers dramatic epithelial cell intercalation events. We show that these cell division-mediated intercalations, which represent the majority of epithelial rearrangements within the early embryo, are absolutely necessary for the spatial patterning of gastrulation movements. Furthermore, we demonstrate that these intercalation events result from overall low cortical actomyosin accumulation within the epithelial cells of the embryo, which enables dividing cells to remodel junctions in their vicinity. These findings uncover a role for cell division as coordinator of epithelial growth and remodeling that might underlie various developmental, homeostatic, or pathological processes in amniotes.

  2. Chromosome catastrophes involve replication mechanisms generating complex genomic rearrangements.

    PubMed

    Liu, Pengfei; Erez, Ayelet; Nagamani, Sandesh C Sreenath; Dhar, Shweta U; Kołodziejska, Katarzyna E; Dharmadhikari, Avinash V; Cooper, M Lance; Wiszniewska, Joanna; Zhang, Feng; Withers, Marjorie A; Bacino, Carlos A; Campos-Acevedo, Luis Daniel; Delgado, Mauricio R; Freedenberg, Debra; Garnica, Adolfo; Grebe, Theresa A; Hernández-Almaguer, Dolores; Immken, LaDonna; Lalani, Seema R; McLean, Scott D; Northrup, Hope; Scaglia, Fernando; Strathearn, Lane; Trapane, Pamela; Kang, Sung-Hae L; Patel, Ankita; Cheung, Sau Wai; Hastings, P J; Stankiewicz, Paweł; Lupski, James R; Bi, Weimin

    2011-09-16

    Complex genomic rearrangements (CGRs) consisting of two or more breakpoint junctions have been observed in genomic disorders. Recently, a chromosome catastrophe phenomenon termed chromothripsis, in which numerous genomic rearrangements are apparently acquired in one single catastrophic event, was described in multiple cancers. Here, we show that constitutionally acquired CGRs share similarities with cancer chromothripsis. In the 17 CGR cases investigated, we observed localization and multiple copy number changes including deletions, duplications, and/or triplications, as well as extensive translocations and inversions. Genomic rearrangements involved varied in size and complexities; in one case, array comparative genomic hybridization revealed 18 copy number changes. Breakpoint sequencing identified characteristic features, including small templated insertions at breakpoints and microhomology at breakpoint junctions, which have been attributed to replicative processes. The resemblance between CGR and chromothripsis suggests similar mechanistic underpinnings. Such chromosome catastrophic events appear to reflect basic DNA metabolism operative throughout an organism's life cycle.

  3. Low-Temperature Cationic Rearrangement in a Bulk Metal Oxide.

    PubMed

    Li, Man-Rong; Retuerto, Maria; Stephens, Peter W; Croft, Mark; Sheptyakov, Denis; Pomjakushin, Vladimir; Deng, Zheng; Akamatsu, Hirofumi; Gopalan, Venkatraman; Sánchez-Benítez, Javier; Saouma, Felix O; Jang, Joon I; Walker, David; Greenblatt, Martha

    2016-08-16

    Cationic rearrangement is a compelling strategy for producing desirable physical properties by atomic-scale manipulation. However, activating ionic diffusion typically requires high temperature, and in some cases also high pressure in bulk oxide materials. Herein, we present the cationic rearrangement in bulk Mn2 FeMoO6 at unparalleled low temperatures of 150-300 (o) C. The irreversible ionic motion at ambient pressure, as evidenced by real-time powder synchrotron X-ray and neutron diffraction, and second harmonic generation, leads to a transition from a Ni3 TeO6 -type to an ordered-ilmenite structure, and dramatic changes of the electrical and magnetic properties. This work demonstrates a remarkable cationic rearrangement, with corresponding large changes in the physical properties in a bulk oxide at unprecedented low temperatures.

  4. Photo-induced and electrooptic properties of (Pb,La)(Zr,Ti)O{sub 3} films

    SciTech Connect

    Dimos, D.; Warren, W.L.; Tuttle, B.A.

    1993-07-01

    Photo-induced changes in the hysteresis behavior of sol-gel derived Pb(Zr,Ti)O{sub 3} (PZT) and (Pb,La)(Zr,Ti)O{sub 3} (PLZT) films have been characterized. Film photosensitivity has been evaluated with respect to magnitude of effects, time response and spectral dependence. Photo-induced hysteresis changes exhibit a stretched-exponential time dependence, which implies a dispersive mechanism. The spectral dependence is strongly peaked at the band edge ({approximately} 3.4 eV), which indicates that generation of electron-hole pairs in the material is critical. The photo-induced hysteresis changes are reproducible and stable, which indicates that the controlling charge traps are stable. However, improvements in film photosensitivity will be required to develop these materials for optical memory applications.

  5. Static and dynamic photoinduced magnetic effects in yttrium-iron garnet lightly doped with barium ions

    SciTech Connect

    Vorob'eva, N. V. Khalilov, R. Z.

    2012-04-15

    In yttrium-iron garnet lightly doped with barium, direct measurements of the photoinduced changes in magnetostrictive strains disagree with those in magnetostriction constants at 78-100 K. This is attributed to a considerable photoinduced modification of the initial state in this sample due to a redistribution of the charge (during illumination) between cations of the ferromagnetic octahedral sublattice. In the same sample, the temperature dependence of the photoinduced disaccomodation of magnetic permeability characterizing the initial demagnetized state is measured and calculated. A change in the electron mechanism of the phenomenon during the transition to room temperature is shown. The conclusion about the promising prospects for using such samples for remagnetization by light is advanced.

  6. Photo-induced Doping in GaN Epilayers with Graphene Quantum Dots

    PubMed Central

    Lin, T. N.; Inciong, M. R.; Santiago, S. R. M. S.; Yeh, T. W.; Yang, W. Y.; Yuan, C. T.; Shen, J. L.; Kuo, H. C.; Chiu, C. H.

    2016-01-01

    We demonstrate a new doping scheme where photo-induced carriers from graphene quantum dots (GQDs) can be injected into GaN and greatly enhance photoluminescence (PL) in GaN epilayers. An 8.3-fold enhancement of PL in GaN is observed after the doping. On the basis of time-resolved PL studies, the PL enhancement is attributed to the carrier transfer from GQDs to GaN. Such a carrier transfer process is caused by the work function difference between GQDs and GaN, which is verified by Kelvin probe measurements. We have also observed that photocurrent in GaN can be enhanced by 23-fold due to photo-induced doping with GQDs. The improved optical and transport properties from photo-induced doping are promising for applications in GaN-based optoelectronic devices. PMID:26987403

  7. Photoinduced Charge Transport in a BHJ Solar Cell Controlled by an External Electric Field

    PubMed Central

    Li, Yongqing; Feng, Yanting; Sun, Mengtao

    2015-01-01

    This study investigated theoretical photoinduced charge transport in a bulk heterojunction (BHJ) solar cell controlled by an external electric field. Our method for visualizing charge difference density identified the excited state properties of photoinduced charge transfer, and the charge transfer excited states were distinguished from local excited states during electronic transitions. Furthermore, the calculated rates for the charge transfer revealed that the charge transfer was strongly influenced by the external electric field. The external electric field accelerated the rate of charge transfer by up to one order when charge recombination was significantly restrained. Our research demonstrated that photoinduced charge transport controlled by an external electric field in a BHJ solar cell is efficient, and the exciton dissociation is not the limiting factor in organic solar cells.Our research should aid in the rational design of a novel conjugated system of organic solar cells. PMID:26353997

  8. Telomerase activation by genomic rearrangements in high-risk neuroblastoma.

    PubMed

    Peifer, Martin; Hertwig, Falk; Roels, Frederik; Dreidax, Daniel; Gartlgruber, Moritz; Menon, Roopika; Krämer, Andrea; Roncaioli, Justin L; Sand, Frederik; Heuckmann, Johannes M; Ikram, Fakhera; Schmidt, Rene; Ackermann, Sandra; Engesser, Anne; Kahlert, Yvonne; Vogel, Wenzel; Altmüller, Janine; Nürnberg, Peter; Thierry-Mieg, Jean; Thierry-Mieg, Danielle; Mariappan, Aruljothi; Heynck, Stefanie; Mariotti, Erika; Henrich, Kai-Oliver; Gloeckner, Christian; Bosco, Graziella; Leuschner, Ivo; Schweiger, Michal R; Savelyeva, Larissa; Watkins, Simon C; Shao, Chunxuan; Bell, Emma; Höfer, Thomas; Achter, Viktor; Lang, Ulrich; Theissen, Jessica; Volland, Ruth; Saadati, Maral; Eggert, Angelika; de Wilde, Bram; Berthold, Frank; Peng, Zhiyu; Zhao, Chen; Shi, Leming; Ortmann, Monika; Büttner, Reinhard; Perner, Sven; Hero, Barbara; Schramm, Alexander; Schulte, Johannes H; Herrmann, Carl; O'Sullivan, Roderick J; Westermann, Frank; Thomas, Roman K; Fischer, Matthias

    2015-10-29

    Neuroblastoma is a malignant paediatric tumour of the sympathetic nervous system. Roughly half of these tumours regress spontaneously or are cured by limited therapy. By contrast, high-risk neuroblastomas have an unfavourable clinical course despite intensive multimodal treatment, and their molecular basis has remained largely elusive. Here we have performed whole-genome sequencing of 56 neuroblastomas (high-risk, n = 39; low-risk, n = 17) and discovered recurrent genomic rearrangements affecting a chromosomal region at 5p15.33 proximal of the telomerase reverse transcriptase gene (TERT). These rearrangements occurred only in high-risk neuroblastomas (12/39, 31%) in a mutually exclusive fashion with MYCN amplifications and ATRX mutations, which are known genetic events in this tumour type. In an extended case series (n = 217), TERT rearrangements defined a subgroup of high-risk tumours with particularly poor outcome. Despite a large structural diversity of these rearrangements, they all induced massive transcriptional upregulation of TERT. In the remaining high-risk tumours, TERT expression was also elevated in MYCN-amplified tumours, whereas alternative lengthening of telomeres was present in neuroblastomas without TERT or MYCN alterations, suggesting that telomere lengthening represents a central mechanism defining this subtype. The 5p15.33 rearrangements juxtapose the TERT coding sequence to strong enhancer elements, resulting in massive chromatin remodelling and DNA methylation of the affected region. Supporting a functional role of TERT, neuroblastoma cell lines bearing rearrangements or amplified MYCN exhibited both upregulated TERT expression and enzymatic telomerase activity. In summary, our findings show that remodelling of the genomic context abrogates transcriptional silencing of TERT in high-risk neuroblastoma and places telomerase activation in the centre of transformation in a large fraction of these tumours.

  9. Ultrafast dynamics during the photoinduced phase transition in VO2

    NASA Astrophysics Data System (ADS)

    Wegkamp, Daniel; Stähler, Julia

    2015-12-01

    The phase transition of VO2 from a monoclinic insulator to a rutile metal, which occurs thermally at TC = 340 K, can also be driven by strong photoexcitation. The ultrafast dynamics during this photoinduced phase transition (PIPT) have attracted great scientific attention for decades, as this approach promises to answer the question of whether the insulator-to-metal (IMT) transition is caused by electronic or crystallographic processes through disentanglement of the different contributions in the time domain. We review our recent results achieved by femtosecond time-resolved photoelectron, optical, and coherent phonon spectroscopy and discuss them within the framework of a selection of latest, complementary studies of the ultrafast PIPT in VO2. We show that the population change of electrons and holes caused by photoexcitation launches a highly non-equilibrium plasma phase characterized by enhanced screening due to quasi-free carriers and followed by two branches of non-equilibrium dynamics: (i) an instantaneous (within the time resolution) collapse of the insulating gap that precedes charge carrier relaxation and significant ionic motion and (ii) an instantaneous lattice potential symmetry change that represents the onset of the crystallographic phase transition through ionic motion on longer timescales. We discuss the interconnection between these two non-thermal pathways with particular focus on the meaning of the critical fluence of the PIPT in different types of experiments. Based on this, we conclude that the PIPT threshold identified in optical experiments is most probably determined by the excitation density required to drive the lattice potential change rather than the IMT. These considerations suggest that the IMT can be driven by weaker excitation, predicting a transiently metallic, monoclinic state of VO2 that is not stabilized by the non-thermal structural transition and, thus, decays on ultrafast timescales.

  10. Recent advances in photoinduced donor/acceptor copolymerization

    NASA Astrophysics Data System (ADS)

    Jönsson, S.; Viswanathan, K.; Hoyle, C. E.; Clark, S. C.; Miller, C.; Morel, F.; Decker, C.

    1999-05-01

    Photoinitiated free radical polymerization of donor (D)/acceptor (A) type monomers has gained considerable interest due to the possibility to efficiently photopolymerize non-acrylate based systems. Furthermore, this photoinduced alternating copolymerization can be accomplished without the presence of a conventional free radical generating photoinitiator. In the past, we have shown that the structural influences in the direct photolysis of N-Alkyl and N-Arylmaleimides as well as their corresponding ground state charge transfer complexes (CTC) with suitable donors have carefully been investigated. For certain combinations of A and D type monomers, a direct photolysis of the ground state complex or the excitation of the acceptor, followed by the formation of an exciplex, has been shown to initiate the copolymerization. Herein, we show that the main route of initiation is based on inter or intra molecular H-abstraction from an excited state maleimide, whereby no exciplex formation takes place. H-abstraction will predominantly take place in systems where easily abstractable hydrogens are present. Our laser flash photolysis investigation, ESR [1] (A. Hiroshi, I. Takasi, T. Nosi, Macromol. Chem. 190 (1989) 2821) and phosphorescence emissions [2,3] (K.S. Chen, T. Foster, J.K.S. Wan, J. Phys. Chem. 84 (1980) 2473; C.J. Seliskar, S.P. McGlynn, J. Chem. Phys. 55 (1971) 4337) studies show that triplet excited states of N-alkyl substituted maleimides (RMI), which are well known strong precursors for direct H-abstractions from aliphatic ethers and secondary alcohols, are formed upon excitation. Rates of copolymerization and degrees of conversion for copolymerization of maleimide/vinyl ether pairs in air and nitrogen have been measured as a function of hydrogen abstractability of the excited triplet state MI as well as the influence of concentration and hydrogen donating effect of the hydrogen donor.

  11. Convergent synthesis and photoinduced processes in multi-chromophoric rotaxanes.

    PubMed

    Megiatto, Jackson D; Li, Ke; Schuster, David I; Palkar, Amit; Herranz, M Ángeles; Echegoyen, Luis; Abwandner, Silke; de Miguel, Gustavo; Guldi, Dirk M

    2010-11-18

    A series of [2]rotaxane materials, in which [60]fullerene is linked to a macrocycle and ferrocene (Fc) moieties are placed at the termini of a thread, both of which possess a central Cu(I)-1,10-phenanthroline [Cu(phen)(2)](+) complex, were synthesized by self-assembly using Sauvage metal template methodology. Two types of threads were constructed, one with terminal ester linkages, and a second with terminal 1,2,3-triazole linkages derived from Cu(I)-catalyzed "click" 1,3-cycloaddition reactions. Model compounds lacking the fullerene moiety were prepared in an analogous manner. The ability of the interlocked Fc-[Cu(phen)(2)](+)-C(60) hybrids to undergo electron transfer upon photoexcitation in benzonitrile, dichloromethane, and ortho-dichlorobenzene was investigated by means of time-resolved fluorescence and transient absorption spectroscopy, using excitation wavelengths directed at the fullerene and [Cu(phen)(2)](+) subunits. The energies of the electronic excited states and charge separated (CS) states that might be formed upon photoexcitation were determined from spectroscopic and electrochemical data. These studies showed that MLCT excited states of the copper complex in the fullerenerotaxanes were quenched by electron transfer to the fullerene in benzonitrile, resulting in charge separated states with oxidized copper and reduced fullerene moieties, (Fc)(2)-[Cu(phen)(2)](2+)-C(60)(•-). Even though electron transfer from Fc to the oxidized copper complex is predicted to be exergonic by 0.16 to 0.20 eV, no unequivocal evidence in support of such a process was obtained. The conclusion that Fc plays no role in the photoinduced processes in our systems rests on the lack of enhancement of the lifetime of the charge separated state, as measured by decay of C(60)(•-) at ∼1000 nm, since one-electron oxidized Fc is very difficult to detect spectroscopically in the 500-800 nm spectral region.

  12. The Amadori Rearrangement for Carbohydrate Conjugation: Scope and Limitations

    PubMed Central

    Hojnik, Cornelia; Müller, Anne; Gloe, Tobias‐Elias

    2016-01-01

    The Amadori rearrangement was investigated for the synthesis of C‐glycosyl‐type neoglycoconjugates. Various amines including diamines, amino‐functionalized glycosides, lysine derivatives, and peptides were conjugated with two different heptoses to generate non‐natural C‐glycosyl‐type glycoconjugates of the d‐gluco and d‐manno series. With these studies, the scope and limitations of the Amadori rearrangement as a conjugation method have been exemplified with respect to the carbohydrate substrate, as well as the amino components. PMID:27840588

  13. Submillisecond organic synthesis: Outpacing Fries rearrangement through microfluidic rapid mixing.

    PubMed

    Kim, Heejin; Min, Kyoung-Ik; Inoue, Keita; Im, Do Jin; Kim, Dong-Pyo; Yoshida, Jun-ichi

    2016-05-06

    In chemical synthesis, rapid intramolecular rearrangements often foil attempts at site-selective bimolecular functionalization. We developed a microfluidic technique that outpaces the very rapid anionic Fries rearrangement to chemoselectively functionalize iodophenyl carbamates at the ortho position. Central to the technique is a chip microreactor of our design, which can deliver a reaction time in the submillisecond range even at cryogenic temperatures. The microreactor was applied to the synthesis of afesal, a bioactive molecule exhibiting anthelmintic activity, to demonstrate its potential for practical synthesis and production.

  14. Rearrangement and evolution of mitochondrial genomes in parrots.

    PubMed

    Eberhard, Jessica R; Wright, Timothy F

    2016-01-01

    Mitochondrial genome rearrangements that result in control region duplication have been described for a variety of birds, but the mechanisms leading to their appearance and maintenance remain unclear, and their effect on sequence evolution has not been explored. A recent survey of mitochondrial genomes in the Psittaciformes (parrots) found that control region duplications have arisen independently at least six times across the order. We analyzed complete mitochondrial genome sequences from 20 parrot species, including representatives of each lineage with control region duplications, to document the gene order changes and to examine effects of genome rearrangements on patterns of sequence evolution. The gene order previously reported for Amazona parrots was found for four of the six independently derived genome rearrangements, and a previously undescribed gene order was found in Prioniturus luconensis, representing a fifth clade with rearranged genomes; the gene order resulting from the remaining rearrangement event could not be confirmed. In all rearranged genomes, two copies of the control region are present and are very similar at the sequence level, while duplicates of the other genes involved in the rearrangement show signs of degeneration or have been lost altogether. We compared rates of sequence evolution in genomes with and without control region duplications and did not find a consistent acceleration or deceleration associated with the duplications. This could be due to the fact that most of the genome rearrangement events in parrots are ancient, and additionally, to an effect of body size on evolutionary rate that we found for mitochondrial but not nuclear sequences. Base composition analyses found that relative to other birds, parrots have unusually strong compositional asymmetry (AT- and GC-skew) in their coding sequences, especially at fourfold degenerate sites. Furthermore, we found higher AT skew in species with control region duplications. One

  15. Supernormal conduction in the anomalous bundles of the Wolff-Parkinson-White syndrome: an overlooked electrophysiologic property with potential clinical implications.

    PubMed

    Chiale, Pablo A; Albino, Ernesto; Garro, Hugo A; Selva, Horacio; Levi, Raúl J; Sánchez, Rubén A; Elizari, Marcelo V; Alvarez, Carlos B

    2007-09-01

    The anterograde refractory period (RP) of the accessory pathway (AP) is the main determinant factor of ventricular rate during atrial fibrillation in the Wolff-Parkinson-White (WPW) syndrome. We describe 3 examples of anterograde supernormal conduction (SNC) and 1 of retrograde SNC in APs. The paradoxical early recovery of propagation due to SNC, well inside a prolonged anterograde RP in the AP, may play a relevant role to determine the rate of ventricular response during atrial fibrillation, eventually leading to extremely fast ventricular rates, syncope, and even ventricular fibrillation in patients with WPW syndrome supposed a priori to be exposed to a low risk of sudden cardiac death. This may require very precise conditions, including an enhanced adrenergic influence on the heart. Retrograde SNC in APs may also participate in the mechanism of paroxysmal supraventricular tachycardias that are not easily induced by programmed cardiac stimulation.

  16. [1:1 atrial flutter in an elderly patient: one of the methods of discovering Wolff-Parkinson-White syndrome. Apropos of a case in an adult].

    PubMed

    Parmeggiani, L; Adamec, R; Perrenoud, J J

    1984-01-01

    Atrial flutter with 1:1 atrioventricular conduction giving rise to a ventricular rhythm of 240/min in an 80 year old man was the first sign of the Wolff-Parkinson-White syndrome; all previous electrocardiogrammes had shown no evidence of pre-excitation. It was only on the fifth day of hospitalisation that the ECG showed a short PR interval with a delta wave. This case illustrates that: --all supraventricular arrhythmias with abnormally high ventricular rates (over 220/min in adults) should alert to the possibility of an accessory atrioventricular pathway; --rapid atrioventricular conduction may be the first sign of an accessory pathway; --the differential diagnosis lies between an accessory atrioventricular pathway and an atriohisian tract; --digitalis, which may shorten the refractory period of the accessory pathway, is contraindicated in patients with a Kent bundle.

  17. [Wolff-Parkinson-White syndrome caused by association of atrio-hisian fibers and Mahaim's fibers. Comparison between the electrophysiology and histology].

    PubMed

    Brechenmacher, C; Courtadon, M; Jourde, M; Yermia, J C; Cheynel, J; Voegtlin, R

    1976-12-01

    A child of six who had had several losses of consciousness died suddenly during a spell of tachycardia. The EKG showed at times a type B Wolff-Parkinson-White syndrome, at times a Lown-Ganong-Levine syndrome. Intracavitary electrophysiological explorations had been carried out. The interest of this case lies in the comparison between these electrophysiological explorations and the histological examination of the normal and accessory conduction pathways. The short PR interval, which did not lengthen under the effect of premature atrial stimulation, was accounted for by the presence of atrio-His bundle tracts. The intermittent delta wave was due to Hissio-ventricular Mahaim fibres. These two accessory conduction pathways are considered as abnormal.

  18. Atrial fibrillation with wide QRS tachycardia and undiagnosed Wolff-Parkinson-White syndrome: diagnostic and therapeutic dilemmas in a pediatric patient.

    PubMed

    Panduranga, Prashanth; Al-Farqani, Abdullah; Al-Rawahi, Najib

    2012-11-01

    A 10-year-old girl presented to the emergency department of a regional hospital with 1 episode of generalized tonic-clonic seizures. Postictal monitoring followed by a 12-lead electrocardiogram showed fast atrial fibrillation with intermittent wide QRS regular tachycardia. Immediately following this, her rhythm changed to wide QRS irregular tachycardia without hemodynamic compromise. She was suspected to have ventricular tachycardia and was treated with intravenous amiodarone with cardioversion to sinus rhythm. Subsequent electrocardiogram in sinus rhythm showed typical features of manifest Wolff-Parkinson-White (WPW) accessory pathway. This case illustrates the diagnostic and therapeutic dilemmas in patients with atrial fibrillation, wide QRS tachycardia, and undiagnosed WPW syndrome with antidromic conduction of atrial arrhythmias through the accessory pathway. Furthermore, this case demonstrates that undiagnosed wide QRS tachycardias need to be treated with drugs acting on the accessory pathway, thus keeping in mind underlying WPW syndrome as a possibility to avoid potentially catastrophic events.

  19. Identification of mtDNA mutation in a pedigree with gestational diabetes, deafness, Wolff-Parkinson-White syndrome and placenta accreta.

    PubMed

    Aggarwal, P; Gill-Randall, R; Wheatley, T; Buchalter, M B; Metcalfe, J; Alcolado, J C

    2001-01-01

    Mitochondrial DNA (mtDNA) defects are associated with a number of human disorders. Although many occur sporadically, maternal transmission is the hallmark of diseases due to mtDNA point mutations. The same mutation may manifest strikingly different phenotypes; for example, the A to G substitution at np 3243 was first reported in patients with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (the MELAS syndrome), but is also found in patients with diabetes and deafness. Here we present a case of gestational diabetes, deafness, premature greying, placenta accreta and Wolff-Parkinson-White (WPW) syndrome associated with a mtDNA mutation. Although this is the first report of such an association, study of 27 other patients with WPW syndrome failed to confirm that this mtDNA mutation is a common cause of such pre-excitation disorders.

  20. Form--a matter of generation: the relation of generation, form, and function in the epigenetic theory of Caspar F. Wolff.

    PubMed

    Witt, Elke

    2008-12-01

    The question, how organisms obtain their specific complex and functional forms, was widely discussed during the eighteenth century. The theory of preformation, which was the dominant theory of generation, was challenged by different alternative epigenetic theories. By the end of the century it was the vitalist approach most famously advocated by Johann Friedrich Blumenbach that prevailed. Yet the alternative theory of generation brought forward by Caspar Friedrich Wolff was an important contribution to the treatment of this question. He turned his attention from the properties of matter and the forces acting on it towards the level of the processes of generation in order to explain the constitution of organismic forms. By regarding organic structures and forms to be the result of the lawfulness of ongoing processes, he opened up the possibility of a functional but non-teleological explanation of generation, and thereby provided an important complement to materialist and vitalist approaches.

  1. Photoinduced reactions of both 2-formyl-2H-azirine and isoxazole: A theoretical study based on electronic structure calculations and nonadiabatic dynamics simulations

    SciTech Connect

    Cao, Jun

    2015-06-28

    In the present work, the combined electronic structure calculations and dynamics simulations have been performed to explore photocleavages of 2-formyl-2H-azirine and isoxazole in the gas phase and the subsequent rearrangement reactions. The carbonyl n → π{sup *} transition induces a cleavage of the C—N single bond of 2-formyl-2H-azirine to yield β-formylvinylnitrene in open-shell singlet state. However, the n → π{sup *} excitation of the imine chromophore results in a cleavage of the C—C single bond, producing a nitrile ylide intermediate through an internal conversion to the ground state. β-formylvinylnitrene and nitrile ylide with the carbonyl group are easily transformed into 2-formyl-2H-azirine and oxazole, respectively. The N—O bond cleavages on both S{sub 1}({sup 1}ππ{sup *}) and S{sub 2}({sup 1}n{sub N}π{sup *}) of isoxazole are ultrafast processes, and they give products of 2-formyl-2H-azirine, 3-formylketenimine, HCN + CHCHO, and HCO + CHCHN. Both 2H-azirines and ketenimines were suggested to be formed from the triplet vinylnitrenes by intersystem crossing in the previous studies. However, our calculations show that the singlet β-formylvinylnitrene is responsible for the formation of 2-formyl-2H-azirine and 3-formylketenimine, and the singlet vinylnitrenes can play a key role in the photoinduced reactions of both 2H-azirines and isoxazoles.

  2. Photoinduced reactions of both 2-formyl-2H-azirine and isoxazole: A theoretical study based on electronic structure calculations and nonadiabatic dynamics simulations

    NASA Astrophysics Data System (ADS)

    Cao, Jun

    2015-06-01

    In the present work, the combined electronic structure calculations and dynamics simulations have been performed to explore photocleavages of 2-formyl-2H-azirine and isoxazole in the gas phase and the subsequent rearrangement reactions. The carbonyl n → π* transition induces a cleavage of the C—N single bond of 2-formyl-2H-azirine to yield β-formylvinylnitrene in open-shell singlet state. However, the n → π* excitation of the imine chromophore results in a cleavage of the C—C single bond, producing a nitrile ylide intermediate through an internal conversion to the ground state. β-formylvinylnitrene and nitrile ylide with the carbonyl group are easily transformed into 2-formyl-2H-azirine and oxazole, respectively. The N—O bond cleavages on both S1(1ππ*) and S2(1nNπ*) of isoxazole are ultrafast processes, and they give products of 2-formyl-2H-azirine, 3-formylketenimine, HCN + CHCHO, and HCO + CHCHN. Both 2H-azirines and ketenimines were suggested to be formed from the triplet vinylnitrenes by intersystem crossing in the previous studies. However, our calculations show that the singlet β-formylvinylnitrene is responsible for the formation of 2-formyl-2H-azirine and 3-formylketenimine, and the singlet vinylnitrenes can play a key role in the photoinduced reactions of both 2H-azirines and isoxazoles.

  3. Photoinduced color centers creation in superionic crystals RbAg 4 I 5

    NASA Astrophysics Data System (ADS)

    Kovaleva, N.; Boris, A.; Bredikhin, S.; Awano, T.

    1995-12-01

    A new phenomenon of a reversible photoinduced coloration caused by light irradiation is discovered and investigated in superionic RbAg 4 I 5 crystals. The reversible photoinduced absorption is found to be a result of irradiation by light with wavelengths in the region from 420 nm to 450 nm. The proposed mechanism of the discovered effect is associated with ambipolar diffusion of screened by mobile ions optically excited electronic carriers. The processes of color centers creation in superionic crystals RbAg 4 I 5 due to additive coloring in iodine vapours, ionic implantation and ?-ray irradiation are considered.

  4. Photoinduced phase transition in tetrathiafulvalene- p -chloranil observed in femtosecond reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Okamoto, H.; Ishige, Y.; Tanaka, S.; Kishida, H.; Iwai, S.; Tokura, Y.

    2004-10-01

    Photoinduced transitions from ionic (I) to neutral (N) and neutral (N) to ionic (I) phases in an organic charge transfer (CT) complex, tetrathiafulvalene- p -chloranil (TTF-CA), were investigated by femtosecond pump-probe reflection spectroscopy. Transient reflectivity changes of the intramolecular transition band of TTF sensitive to the degree of CT between a donor molecule of TTF and an acceptor molecule of CA are measured as a function of excitation energy, excitation density, and temperature. By adopting the multilayer model for the analysis of the obtained transient reflectivity spectra, we have derived the time characteristics of amounts and spatial distributions of photoinduced N(I) states in the I(N) phase. The results reveal that the I to N(IN) transition induced by the resonant excitation of the CT band at 4K is composed of three processes; (1) formation of a confined one-dimensional (1D) N domain, that is, a sequence of D0A0 pairs, just after the photoexcitation, (2) multiplication of the 1D N domains to the semimacroscopic N states up to 20ps within the absorption depth of the excitation light, and (3) proceeding of the IN transition along the direction normal to the sample surface. At 77K near the NI transition temperature (Tc=81K) , the size of the 1D N domain initially produced is enlarged and its multiplication process is strongly enhanced. When the excitation energy is increased, the initial photoproduct is changed from the confined 1D N domain to the positively and negatively charged N states. The spatial size of the latter is considerably larger than that of the former, indicating that the introduction of charge carriers makes the neighboring I state strongly unstable. The dynamics of the photoinduced N to I(NI) transition has also been investigated. The 1D I domains are initially produced by lights, however, they decay within 20ps even if the density of the I domains is increased. The results demonstrate that there is a clear difference of the

  5. Determination of photoinduced and intrinsic birefringences in PMMA/DR13 guest-host film

    NASA Astrophysics Data System (ADS)

    Dall'Agnol, Fernando Fuzinatto; Shimizu, Flávio Makoto; Giacometti, José A.

    2014-07-01

    We report measurements and analysis of photoinduced birefringence (PIB) in polymeric stretched films, hence, with an intrinsic birefringence (IB) associated to the polymeric chain orientation. It was found that transmittance signal is dependent on the angle between the film stretching direction and the probe light polarization, increasing or decreasing relatively to IB signal. Theoretical analysis considered that light propagates through the film having a photoinduced and intrinsic birefringences with independent optical axes. The transmittance signal dependence on the film angle is correctly accounted and our approach could give a phenomenological elucidation to the effect known as the inverse relaxation effect.

  6. Stretched exponential kinetics for photoinduced birefringence in azo dye doped PVA films

    NASA Astrophysics Data System (ADS)

    Yang, Hye Ri; Kim, Eun Ju; Lee, Sang Jo; Kim, Gun Yeup; Kwak, Chong Hoon

    2009-05-01

    We fabricated azo dye (methylorange) doped poly vinyl alcohol (MO/PVA) thin films and measured the photoinduced birefringence (PIB) kinetics for several pump beam intensities and for various MO concentrations by using the pump-probe technique. A novel approach to explain the transient behaviors of the photoinduced anisotropy is presented by employing an empirical stretched exponential time response in the course of the trans-cis-trans photoisomerization of azo molecules and is compared with the experimental data, showing excellent agreement. The stretched exponent is estimated to be β = 0.34 ± 0.04, revealing amorphous nature of the MO/PVA system.

  7. Qsars for photoinduced toxicity: 1. acute lethality of polycyclic aromatic hydrocarbons to daphnia magna'

    SciTech Connect

    Mekenyan, O.G.; Ankley, G.T.; Veith, G.D.; Call, D.J.

    1994-01-01

    Research with a variety of aquatic species has shown that while polycyclic aromatic hydrocarbons (PAHs) are generally not acutely toxic in conventional laboratory tests, many are extremely toxic in the presence of sunlight. In an effort to develop a model for predicting which PAHs may exhibit photo-induced toxicity, Newsted and Giesy (1987) reported a parabolic relationship between the toxicity and the energy of the triplet state of a variety of PAHs. The authors have reexamined these data and propose a more mechanistic explanation for the prediction of photo-induced PAH toxicity. They sought a molecular descriptor which could be computed from structure rather than measured empirically.

  8. Novel mechanism of photoinduced reversible phase transitions in molecule-based magnets.

    PubMed

    Kawamoto, T; Asai, Y; Abe, S

    2001-01-08

    A novel microscopic mechanism of bidirectional structural changes is proposed for the photoinduced magnetic phase transition in Co-Fe Prussian blue analogs on the basis of ab initio quantum chemical cluster calculations. It is shown that the local potential energies of various spin states of Co are sensitive to the number of nearest neighbor Fe vacancies. As a result, the forward and backward structural changes are most readily initiated by excitation of different local regions by different photons. This mechanism suggests an effective strategy to realize photoinduced reversible phase transitions in a general system consisting of two local components.

  9. Band Structure Simulations of the Photoinduced Changes in the MgB2:Cr Films

    PubMed Central

    Kityk, Iwan V.; Fedorchuk, Anatolii O.; Ozga, Katarzyna; AlZayed, Nasser S.

    2015-01-01

    An approach for description of the photoinduced nonlinear optical effects in the superconducting MgB2:Cr2O3 nanocrystalline film is proposed. It includes the molecular dynamics step-by-step optimization of the two separate crystalline phases. The principal role for the photoinduced nonlinear optical properties plays nanointerface between the two phases. The first modified layers possess a form of slightly modified perfect crystalline structure. The next layer is added to the perfect crystalline structure and the iteration procedure is repeated for the next layer. The total energy here is considered as a varied parameter. To avoid potential jumps on the borders we have carried out additional derivative procedure.

  10. The nature of photoinduced changes in the magnetostriction of yttrium-iron garnet single crystals

    SciTech Connect

    Vorob'eva, N. V.

    2011-05-15

    A model of the occurrence of photoinduced changes in linear magnetostriction is proposed based on a complex experimental study of magnetostrictive strains in yttrium-iron garnets Y{sub 3}Fe{sub 5}O{sub 12} with low contents of different impurities. Analytical expressions for calculating the magnetostriction in yttrium-iron garnet single crystals with different types of doping are presented. The correlation of the photoinduced change in the magnetostriction with the crystallographic features of the samples is demonstrated. The changes in the magnetostriction constants are analyzed quantitatively for samples prepared in different ways.

  11. Photoinduced adsorption of hydrogen and methane on gamma-alumina. the photoinduced chesorluminescence (PhICL) effect.

    PubMed

    Andreev, N S; Emeline, A V; Polikhova, S V; Ryabchuk, V K; Serpone, N

    2004-01-06

    Adsorption of hydrogen and methane on a preirradiated surface of gamma-Al2O3 produces an afterglow, which has been described as a photoinduced chesorluminescence (PhICL), whose spectral features identify with the intrinsic photoluminescence of alumina. The emission spectrum consists of at least four overlapping single emission bands. For methane adsorption, the PhICL phenomenon is seen only if the solid is preirradiated in the presence of oxygen. Emission decay kinetics of the PhICL effect for gamma-Al2O3 reveal two wavelength regimes: a short wavelength regime at lambda = 300-370 nm (decay time tau = 1.1 +/- 0.2 s; signal width = 2.8 s), and a longer wavelength regime at lambda = 380-700 nm (decay time tau = 2.1 +/- 0.1 s; signal width = 4.3 s). A model is proposed in which there exist two different emission centers and, thus, two different pathways for emission decay. In the first, emission originates with electron trapping by such deep energy traps as anion vacancies {e- + Va --> F+ + hv1} to yield electron F-type color centers, whereas in the second, emission originates from electron/trapped hole recombination {e- + Os*- --> Os2- + hv2}. The first common step of the pathways is homolytic dissociative chemisorption of hydrogen and methane upon interaction with surface-active hole centers Os*-, produced upon preirradiation of alumina, to give atomic hydrogen H* and methyl radicals CH3*. Thermoprogrammed desorption spectra of photoadsorbed or postsorbed oxygen show that adsorbed oxygen interacts with atomic hydrogen and methyl radicals. The products of thermodesorption were H2O for hydrogen and H2O, CO2, and CH3CH3 for methane. The Solonitsyn memory effect coefficient was also evaluated for oxygen photoadsorption.

  12. Radical [1,3]-Rearrangements of Breslow Intermediates

    PubMed Central

    Alwarsh, Sefat; Xu, Yi; Qian, Steven

    2015-01-01

    Breslow intermediates that bear radical stabilizing N-substituents including benzyl, cinnamyl, and diarylmethyl undergo facile homolytic C-N bond scission under mild conditions to give products of formal [1,3]-rearrangement rather than benzoin condensation. EPR experiments and computational analysis support a radical mechanism. Implications for thiamine based enzymes are discussed. PMID:26553753

  13. Computational Analysis of Stereospecificity in the Cope Rearrangement

    ERIC Educational Resources Information Center

    Glish, Laura; Hanks, Timothy W.

    2007-01-01

    The Cope rearrangement is a highly stereospecific, concerted reaction of considerable synthetic utility. Experimental product distributions from the reaction of disubstituted 1,5-hexadienes can be readily understood by computer modeling of the various possible transitions states. Semi-empirical methods give relative energies of transition states…

  14. Si-free enolate Claisen rearrangements of enamido substrates.

    PubMed

    Harker, Wesley R R; Carswell, Emma L; Carbery, David R

    2012-02-21

    α-Alkyl β-amino esters are available in high diastereoselectivity through a silicon-free Claisen enolate [3,3]-sigmatropic rearrangement of enamide esters. Optimisation studies have probed the crucial role of the initial enolisation and the nature of the enamide N-centre. The demonstration of chirality transfer and the formation of β-proline systems, is also presented.

  15. Gold-catalysed cascade rearrangements of ynamide propargyl esters.

    PubMed

    Heffernan, Stephen J; Beddoes, James M; Mahon, Mary F; Hennessy, Alan J; Carbery, David R

    2013-03-21

    The Au(I)-catalysed rearrangement of propargylic esters formed from an ynamide has been studied. The reaction is facile, and when conducted in the presence of a reactive indole nucleophile, leads to a cascade process whereby γ-indolyl α-acyloxyenamides are formed in good yield and excellent E-stereoselectivity.

  16. The Basel Problem as a Rearrangement of Series

    ERIC Educational Resources Information Center

    Benko, David; Molokach, John

    2013-01-01

    We give an elementary solution to the famous Basel Problem, originally solved by Euler in 1735. We square the well-known series for arctan(1) due to Leibniz, and use a surprising relation among the re-arranged terms of this squared series.

  17. Stochastic rearrangement of immunoglobulin variable-region genes in chicken B-cell development.

    PubMed

    Benatar, T; Tkalec, L; Ratcliffe, M J

    1992-08-15

    The molecular mechanism by which immunoglobulin (Ig) gene rearrangement occurs is highly conserved between mammalian and avian species. However, in avian species, an equivalent to the mammalian pre-B cell, which has undergone Ig heavy-chain gene rearrangement and expresses mu heavy chains in the absence of Ig light-chain rearrangement, has not been convincingly demonstrated. It is consequently unclear whether an ordered progression of gene rearrangement events leading to functional Ig expression occurs in avian species. To examine the sequence of Ig gene rearrangement events in chicken B-cell development, we transformed day 12 embryo bursal cells with the REV-T(CSV) retrovirus. More than 100 clones were analyzed by Southern blotting and polymerase chain reaction for the presence of Ig gene rearrangements. The majority of these clones contained only germline Ig sequences. Several clones contained complete heavy- and light-chain rearrangements and 13 clones contained only heavy-chain rearrangements analogous to stages of mammalian B-cell development. However, 5 clones contained rearrangements of light-chain genes in the absence of complete heavy-chain rearrangement. Consequently, we conclude that rearrangement of chicken Ig light-chain genes does not require heavy-chain variable-region rearrangement. This observation suggests that chicken Ig gene rearrangement events required for Ig expression occur stochastically rather than sequentially.

  18. Photoinduced bimolecular electron transfer kinetics in small unilamellar vesicles

    SciTech Connect

    Choudhury, Sharmistha Dutta; Kumbhakar, Manoj; Nath, Sukhendu; Pal, Haridas

    2007-11-21

    Photoinduced electron transfer (ET) from N,N-dimethylaniline to some coumarin derivatives has been studied in small unilamellar vesicles (SUVs) of the phospholipid, DL-{alpha}-dimyristoyl-phosphatidylcholine, using steady-state and time-resolved fluorescence quenching, both below and above the phase transition temperature of the vesicles. The primary interest was to examine whether Marcus inversion [H. Sumi and R. A. Marcus, J. Chem. Phys. 84, 4894 (1986)] could be observed for the present ET systems in these organized assemblies. The influence of the topology of SUVs on the photophysical properties of the reactants and consequently on their ET kinetics has also been investigated. Absorption and fluorescence spectral data of the coumarins in SUVs and the variation of their fluorescence decays with temperature indicate that the dyes are localized in the bilayer of the SUVs. Time-resolved area normalized emission spectra analysis, however, reveals that the dyes are distributed in two different microenvironments in the SUVs, which we attribute to the two leaflets of the bilayer, one toward bulk water and the other toward the inner water pool. The microenvironments in the two leaflets are, however, not indicated to be that significantly different. Time-resolved anisotropy decays were biexponential for all the dyes in SUVs, and this has been interpreted in terms of the compound motion model according to which the dye molecules can experience a fast wobbling-in-cone type of motion as well as a slow overall rotating motion of the cone containing the molecule. The expected bimolecular diffusion-controlled rates in SUVs, as estimated by comparing the microviscosities in SUVs (determined from rotational correlation times) and that in acetonitrile solution, are much slower than the observed fluorescence quenching rates, suggesting that reactant diffusion (translational) does not play any role in the quenching kinetics in the present systems. Accordingly, clear inversions are

  19. Photoinduced axial ligation and deligation dynamics of nonplanar nickel dodecaarylporphyrins.

    PubMed

    Retsek, Jennifer L; Drain, Charles Michael; Kirmaier, Christine; Nurco, Daniel J; Medforth, Craig J; Smith, Kevin M; Sazanovich, Igor V; Chirvony, Vladimir S; Fajer, Jack; Holten, Dewey

    2003-08-13

    and open new avenues for exploring photoinduced ligand association and dissociation behavior.

  20. Hetero-cycloreversions mediated by photoinduced electron transfer.

    PubMed

    Pérez-Ruiz, Raúl; Jiménez, M Consuelo; Miranda, Miguel A

    2014-04-15

    Discovered more than eight decades ago, the Diels-Alder (DA) cycloaddition (CA) remains one of the most versatile tools in synthetic organic chemistry. Hetero-DA processes are powerful methods for the synthesis of densely functionalized six-membered heterocycles, ubiquitous substructures found in natural products and bioactive compounds. These reactions frequently employ azadienes and oxadienes, but only a few groups have reported DA processes with thiadienes. The electron transfer (ET) version of the DA reaction, though less investigated, has emerged as a subject of increasing interest. In the last two decades, researchers have paid closer attention to radical ionic hetero-cycloreversions, mainly in connection with their possible involvement in the repair of pyrimidine(6-4)pyrimidone photolesions in DNA by photolyases. In biological systems, these reactions likely occur through a reductive photosensitization mechanism. In addition, photooxidation can lead to cycloreversion (CR) reactions, and researchers can exploit this strategy for DNA repair therapies. In this Account, we discuss electron-transfer (ET) mediated hetero-CR reactions. We focus on the oxidative and reductive ET splitting of oxetanes, azetidines, and thietanes. Photoinduced electron transfer facilitates the splitting of a variety of four-membered heterocycles. In this context, researchers have commonly examined oxetanes, both experimentally and theoretically. Although a few studies have reported the cycloreversion of azetidines and thietanes carried out under electron transfer conditions, the number of examples remains limited. In general, the cleavage of the ionized four-membered rings appears to occur via a nonconcerted two-step mechanism. The trapping of the intermediate 1,4-radical ions and transient absorption spectroscopy data support this hypothesis, and it explains the observed loss of stereochemistry in the products. In the initial step, either C-C or C-X bond breaking may occur, and the

  1. Revising Intramolecular Photoinduced Electron Transfer (PET) from First-Principles.

    PubMed

    Escudero, Daniel

    2016-09-20

    Photoinduced electron transfer (PET) plays relevant roles in many areas of chemistry, including charge separation processes in photovoltaics, natural and artificial photosynthesis, and photoluminescence sensors and switches. As in many other photochemical scenarios, the structural and energetic factors play relevant roles in determining the rates and efficiencies of PET and its competitive photodeactivation processes. Particularly, in the field of fluorescent sensors and switches, intramolecular PET is believed (in many cases without compelling experimental proof) to be responsible of the quench of fluorescence. There is an increasing experimental interest in fluorophore's molecular design and on achieving optimal excitation/emission spectra, excitation coefficients, and fluorescence quantum yields (importantly for bioimaging purposes), but less efforts are devoted to fundamental mechanistic studies. In this Account, I revise the origins of the fluorescence quenching in some of these systems with state-of-the-art quantum chemical tools. These studies go beyond the common strategy of analyzing frontier orbital energy diagrams and performing PET thermodynamics calculations. Instead, the potential energy surfaces (PESs) of the lowest-lying excited states are explored with time-dependent density functional theory (TD-DFT) and complete active space self-consistent field (CASSCF) calculations and the radiative and nonradiative decay rates from the involved excited states are computed from first-principles using a thermal vibration correlation function formalism. With such a strategy, this work reveals the real origins of the fluorescence quenching, herein entitled as dark-state quenching. Dark states (those that do not absorb or emit light) are often elusive to experiments and thus, computational investigations can provide novel insights into the actual photodeactivation mechanisms. The success of the dark-state quenching mechanism is demonstrated for a wide variety of

  2. Tissue cohesion and the mechanics of cell rearrangement.

    PubMed

    David, Robert; Luu, Olivia; Damm, Erich W; Wen, Jason W H; Nagel, Martina; Winklbauer, Rudolf

    2014-10-01

    Morphogenetic processes often involve the rapid rearrangement of cells held together by mutual adhesion. The dynamic nature of this adhesion endows tissues with liquid-like properties, such that large-scale shape changes appear as tissue flows. Generally, the resistance to flow (tissue viscosity) is expected to depend on the cohesion of a tissue (how strongly its cells adhere to each other), but the exact relationship between these parameters is not known. Here, we analyse the link between cohesion and viscosity to uncover basic mechanical principles of cell rearrangement. We show that for vertebrate and invertebrate tissues, viscosity varies in proportion to cohesion over a 200-fold range of values. We demonstrate that this proportionality is predicted by a cell-based model of tissue viscosity. To do so, we analyse cell adhesion in Xenopus embryonic tissues and determine a number of parameters, including tissue surface tension (as a measure of cohesion), cell contact fluctuation and cortical tension. In the tissues studied, the ratio of surface tension to viscosity, which has the dimension of a velocity, is 1.8 µm/min. This characteristic velocity reflects the rate of cell-cell boundary contraction during rearrangement, and sets a limit to rearrangement rates. Moreover, we propose that, in these tissues, cell movement is maximally efficient. Our approach to cell rearrangement mechanics links adhesion to the resistance of a tissue to plastic deformation, identifies the characteristic velocity of the process, and provides a basis for the comparison of tissues with mechanical properties that may vary by orders of magnitude.

  3. Photoinduced electron transfer from rail to rung within a self-assembled oligomeric porphyrin ladder

    SciTech Connect

    She, Chunxing; Lee, Suk Joong; McGarrah, James E.; Vura-Weis, Josh; Wasielewski, Michael; Chen, Hanning; Schatz, George C.; Ratner, Mark A.; Hupp, Joseph T.

    2010-01-01

    Photoinduced electron transfer in a self-assembled supramolecular ladder structure comprising oligomeric porphyrin rails and ligated dipyridyltetrazine rungs was characterized by transient absorption spectroscopy and transient direct current photoconductivity to be mainly from an oligomer (rail) to the center of a terminal tetrazine (rung), with the remaining hole being delocalized on the oligomer and subsequent charge recombination in 0.19 ns.

  4. Distance dependence in photoinduced intramolecular electron transfer. Additional remarks and calculations

    NASA Astrophysics Data System (ADS)

    Larsson, Sven; Volosov, Andrey

    1987-12-01

    Rate constants for photoinduced intramolecular electron transfer are calculated for four of the molecules studied by Hush et al. The electronic factor is obtained in quantum chemical calculations using the CNDO/S method. The results agree reasonably well with experiments for the forward reaction. Possible reasons for the disagreement for the charge recombination process are offered.

  5. Photoinduced refractive index change and absorption bleaching in poly(methylphenylsilane) under varied atmospheres.

    SciTech Connect

    Potter, Barrett George, Jr.; Simmons-Potter, Kelly; Chandra, Haripin; Thomes, William Joseph, Jr.; Jamison, Gregory Marks

    2005-06-01

    Polysilane materials exhibit large photo-induced refractive index changes under low incident optical fluences, making them attractive candidates for applications in which rapid patterning of photonic device structures is desired immediately prior to their use. This agile fabrication strategy for integrated photonics inherently requires that optical exposure, and associated material response, occurs in nonlaboratory environments, motivating the study of environmental conditions on the photoinduced response of the material. The present work examines the impact of atmosphere on the photosensitive response of poly(methylphenylsilane) (PMPS) thin films in terms of both photoinduced absorption change and refractive index modification. Material was subjected to UV light exposure resonant with the lowest energy optical transition associated with the conjugated Si-Si backbone. Exposures were performed in both aerobic and anaerobic atmospheres (oxygen, air, nitrogen, and 5% H{sub 2}/95% N{sub 2}). The results clearly demonstrate that the photosensitive response of this model polysilane material was dramatically affected by local environment, exhibiting a photoinduced refractive index change, when exposed under an oxygen containing atmosphere, that was twice that observed under anaerobic conditions. This effect is discussed in terms of photo-oxidation processes within the polysilane structure and in the context of the need for predictable photosensitive refractive index change in varied photoimprinting environments.

  6. EFFECT OF IRRADIANCE SPECTRA ON THE PHOTOINDUCED TOXICITY OF THREE POLYCYCLIC AROMATIC HYDROCARBONS

    EPA Science Inventory

    Photoinduced toxicity of polycyclic aromatic hydrocarbons (PAHs) is dependent on the concentration of compounds present and the dose of light received. Of the light present, only those wavelengths absorbed by the compound have the potential to initiate the photochemical events un...

  7. Development of the Ireland-Claisen rearrangement of alkoxy- and aryloxy-substituted allyl glycinates.

    PubMed

    Tellam, James P; Carbery, David R

    2010-11-19

    The Ireland-Claisen rearrangement of 3-alkoxy- and 3-aryloxy-substituted allyl glycinates is presented. This [3,3]-sigmatropic rearrangement route offers direct access to syn β-alkoxy and β-aryloxy α-amino acid systems. In particular, N,N-diboc glycine esters rearrange with excellent diastereoselectivities (dr > 25:1). The synthesis of substrates, rearrangement optimization, and a discussion of stereoselection are presented.

  8. Chemical Detection Based on Adsorption-Induced and Photo-Induced Stresses in MEMS Devices

    SciTech Connect

    Datskos, P.G.

    1999-04-05

    Recently there has been an increasing demand to perform real-time in-situ chemical detection of hazardous materials, contraband chemicals, and explosive chemicals. Currently, real-time chemical detection requires rather large analytical instrumentation that are expensive and complicated to use. The advent of inexpensive mass produced MEMS (micro-electromechanical systems) devices opened-up new possibilities for chemical detection. For example, microcantilevers were found to respond to chemical stimuli by undergoing changes in their bending and resonance frequency even when a small number of molecules adsorb on their surface. In our present studies, we extended this concept by studying changes in both the adsorption-induced stress and photo-induced stress as target chemicals adsorb on the surface of microcantilevers. For example, microcantilevers that have adsorbed molecules will undergo photo-induced bending that depends on the number of absorbed molecules on the surface. However, microcantilevers that have undergone photo-induced bending will adsorb molecules on their surfaces in a distinctly different way. Depending on the photon wavelength and microcantilever material, the microcantilever can be made to bend by expanding or contracting the irradiated surface. This is important in cases where the photo-induced stresses can be used to counter any adsorption-induced stresses and increase the dynamic range. Coating the surface of the microstructure with a different material can provide chemical specificity for the target chemicals. However, by selecting appropriate photon wavelengths we can change the chemical selectivity due to the introduction of new surface states in the MEMS device. We will present and discuss our results on the use of adsorption-induced and photo-induced bending of microcantilevers for chemical detection.

  9. Nucleotide resolution analysis of TMPRSS2 and ERG rearrangements in prostate cancer

    PubMed Central

    Weier, Christopher; Haffner, Michael C.; Mosbruger, Timothy; Esopi, David M.; Hicks, Jessica; Zheng, Qizhi; Fedor, Helen; Isaacs, William B.; De Marzo, Angelo M.; Nelson, William G.; Yegnasubramanian, Srinivasan

    2013-01-01

    TMPRSS2-ERG rearrangements occur in approximately 50% of prostate cancers and therefore represent one of the most frequently observed structural rearrangements in all cancers. However, little is known about the genomic architecture of such rearrangements. We therefore designed and optimized a pipeline involving target-capture of TMPRSS2 and ERG genomic sequences coupled with paired-end next generation sequencing to resolve genomic rearrangement breakpoints in TMPRSS2 and ERG at nucleotide resolution in a large series of primary prostate cancer specimens (n = 83). This strategy showed >90% sensitivity and specificity in identifying TMPRSS2-ERG rearrangements, and allowed identification of intra- and inter-chromosomal rearrangements involving TMPRSS2 and ERG with known and novel fusion partners. Our results indicate that rearrangement breakpoints show strong clustering in specific intronic regions of TMPRSS2 and ERG. The observed TMPRSS2-ERG rearrangements often exhibited complex chromosomal architecture associated with several intra- and inter-chromosomal rearrangements. Nucleotide resolution analysis of breakpoint junctions revealed that the majority of TMPRSS2 and ERG rearrangements (~88%) occurred at or near regions of microhomology or involved insertions of one or more base pairs. This architecture implicates nonhomologous end joining (NHEJ) and microhomology mediated end joining (MMEJ) pathways in the generation of such rearrangements. These analyses have provided important insights into the molecular mechanisms involved in generating prostate cancer-specific recurrent rearrangements. PMID:23447416

  10. RNA-Mediated Epigenetic Programming of Genome Rearrangements

    PubMed Central

    Nowacki, Mariusz; Shetty, Keerthi; Landweber, Laura F.

    2012-01-01

    RNA, normally thought of as a conduit in gene expression, has a novel mode of action in ciliated protozoa. Maternal RNA templates provide both an organizing guide for DNA rearrangements and a template that can transport somatic mutations to the next generation. This opportunity for RNA-mediated genome rearrangement and DNA repair is profound in the ciliate Oxytricha, which deletes 95% of its germline genome during development in a process that severely fragments its chromosomes and then sorts and reorders the hundreds of thousands of pieces remaining. Oxytricha’s somatic nuclear genome is therefore an epigenome formed through RNA templates and signals arising from the previous generation. Furthermore, this mechanism of RNA-mediated epigenetic inheritance can function across multiple generations, and the discovery of maternal template RNA molecules has revealed new biological roles for RNA and has hinted at the power of RNA molecules to sculpt genomic information in cells. PMID:21801022

  11. Chromosome-specific staining to detect genetic rearrangements

    DOEpatents

    Gray, Joe W.; Pinkel, Daniel; Tkachuk, Douglas; Westbrook, Carol

    2013-04-09

    Methods and compositions for staining based upon nucleic acid sequence that employ nucleic acid probes are provided. Said methods produce staining patterns that can be tailored for specific cytogenetic analyzes. Said probes are appropriate for in situ hybridization and stain both interphase and metaphase chromosomal material with reliable signals. The nucleic acid probes are typically of a complexity greater than 50 kb, the complexity depending upon the cytogenetic application. Methods and reagents are provided for the detection of genetic rearrangements. Probes and test kits are provided for use in detecting genetic rearrangements, particularly for use in tumor cytogenetics, in the detection of disease related loci, specifically cancer, such as chronic myelogenous leukemia (CML) and for biological dosimetry. Methods and reagents are described for cytogenetic research, for the differentiation of cytogenetically similar but genetically different diseases, and for many prognostic and diagnostic applications.

  12. Incremental exposure facilitates adaptation to sensory rearrangement. [vestibular stimulation patterns

    NASA Technical Reports Server (NTRS)

    Lackner, J. R.; Lobovits, D. N.

    1978-01-01

    Visual-target pointing experiments were performed on 24 adult volunteers in order to compare the relative effectiveness of incremental (stepwise) and single-step exposure conditions on adaptation to visual rearrangement. The differences between the preexposure and postexposure scores served as an index of the adaptation elicited during the exposure period. It is found that both single-step and stepwise exposure to visual rearrangement elicit compensatory changes in sensorimotor coordination. However, stepwise exposure, when compared to single-step exposur in terms of the average magnitude of visual displacement over the exposure period, clearly enhances the rate of adaptation. It seems possible that the enhancement of adaptation to unusual patterns of sensory stimulation produced by incremental exposure reflects a general principle of sensorimotor function.

  13. Wolff-Parkinson-White syndrome type B with tachycardia-dependent (phase 3) block in the accessory pathway and in left bundle-branch coexisting with rate-unrelated right bundle-branch block.

    PubMed Central

    Mendoza, I J; Castellanos, A; Sung, R J

    1980-01-01

    A patient with Wolff-Parkinson-White syndrome type B developed 2:1 atrioventricular block resulting from the association of persistent right bundle-branch block with tachycardia-dependent (phase 3) left bundle-branch block. Electrophysiological studies disclosed the coexistence of a tachycardia-dependent (phase 3) block in the accessory pathway. This conduction disturbance was exposed, not by carotid sinus massage as in previous studies, but by pacing-induced prolongation of the interval between two consecutively conducted atrial impulses. Furthermore, the surface electrocardiogram showed, at different times, ventricular complexes resulting from: (1) exclusive atrioventricular conduction through the normal pathway without bundle-branch block; (2) predominant, or exclusive, atrioventricular conduction through a right-sided accessory pathway; (3) exclusive atrioventricular conduction through the normal pathway with right bundle-branch block; (4) exclusive conduction through the normal pathway, with left bundle-branch block; (5) fusion between (1) and (2); and finally, (6) fusion between (2) and (3) However, QRS complexes resulting from simultaneously occurring Wolff-Parkinson-White syndrome type B and left bundle-branch block could not be identified. Future electrophysiological investigations should re-evaluate the criteria used to diffrentiate between true and false patterns of Wolff-Parkinson-White syndrome type B coexisting with left bundle-branch block. PMID:7397051

  14. Chromosomal rearrangements maintain a polymorphic supergene controlling butterfly mimicry

    PubMed Central

    Joron, Mathieu; Frezal, Lise; Jones, Robert T.; Chamberlain, Nicola L.; Lee, Siu F.; Haag, Christoph R.; Whibley, Annabel; Becuwe, Michel; Baxter, Simon W.; Ferguson, Laura; Wilkinson, Paul A.; Salazar, Camilo; Davidson, Claire; Clark, Richard; Quail, Michael A.; Beasley, Helen; Glithero, Rebecca; Lloyd, Christine; Sims, Sarah; Jones, Matthew C.; Rogers, Jane; Jiggins, Chris D.; ffrench-Constant, Richard H.

    2013-01-01

    Supergenes are tight clusters of loci that facilitate the co-segregation of adaptive variation, providing integrated control of complex adaptive phenotypes1. Polymorphic supergenes, in which specific combinations of traits are maintained within a single population, were first described for ‘pin’ and ‘thrum’ floral types in Primula1 and Fagopyrum2, but classic examples are also found in insect mimicry3–5 and snail morphology6. Understanding the evolutionary mechanisms that generate these co-adapted gene sets, as well as the mode of limiting the production of unfit recombinant forms, remains a substantial challenge7–10. Here we show that individual wing-pattern morphs in the polymorphic mimetic butterfly Heliconius numata are associated with different genomic rearrangements at the supergene locus P. These rearrangements tighten the genetic linkage between at least two colour-pattern loci that are known to recombine in closely related species9–11, with complete suppression of recombination being observed in experimental crosses across a 400-kilobase interval containing at least 18 genes. In natural populations, notable patterns of linkage disequilibrium (LD) are observed across the entire P region. The resulting divergent haplotype clades and inversion breakpoints are found in complete association with wing-pattern morphs. Our results indicate that allelic combinations at known wing-patterning loci have become locked together in a polymorphic rearrangement at the Plocus, forming a supergene that acts as a simple switch between complex adaptive phenotypes found in sympatry. These findings highlight how genomic rearrangements can have a central role in the coexistence of adaptive phenotypes involving several genes acting in concert, by locally limiting recombination and gene flow. PMID:21841803

  15. Recent applications of ring-rearrangement metathesis in organic synthesis.

    PubMed

    Kotha, Sambasivarao; Meshram, Milind; Khedkar, Priti; Banerjee, Shaibal; Deodhar, Deepak

    2015-01-01

    Ring-rearrangement metathesis (RRM) involves multiple metathesis processes such as ring-opening metathesis (ROM)/ring-closing metathesis (RCM) in a one-pot operation to generate complex targets. RRM delivers complex frameworks that are difficult to assemble by conventional methods. The noteworthy point about this type of protocol is multi-bond formation and it is an atom economic process. In this review, we have covered literature that appeared during the last seven years (2008-2014).

  16. Pyridine to aniline: an exceptional biologically driven rearrangement.

    PubMed

    Arnauld, Thomas; Beaumal, Jean-Yves; Lefoulon, François; Petit, Alain; Renaud, Tristan

    2013-04-01

    During the course of our study on the innovative ligand for nicotinic acetylcholinergic receptors, LNAChR, and in order to assess activity and toxicity profiles of the drug's metabolites, synthesis of the main metabolites was undertaken. This synthesis work was done in parallel by organic chemistry and by biotransformation of LNAChR. Filamentous fungus Aspergillus alliaceus (NRRL 315) neatly afforded three of the main metabolites, one of which arose from a very unexpected and very uncommon rearrangement.

  17. Recent applications of ring-rearrangement metathesis in organic synthesis

    PubMed Central

    Meshram, Milind; Khedkar, Priti; Banerjee, Shaibal; Deodhar, Deepak

    2015-01-01

    Summary Ring-rearrangement metathesis (RRM) involves multiple metathesis processes such as ring-opening metathesis (ROM)/ring-closing metathesis (RCM) in a one-pot operation to generate complex targets. RRM delivers complex frameworks that are difficult to assemble by conventional methods. The noteworthy point about this type of protocol is multi-bond formation and it is an atom economic process. In this review, we have covered literature that appeared during the last seven years (2008–2014). PMID:26664603

  18. Quantifying stretching and rearrangement in epithelial sheet migration.

    PubMed

    Lee, Rachel M; Kelley, Douglas H; Nordstrom, Kerstin N; Ouellette, Nicholas T; Losert, Wolfgang

    2013-02-25

    Although understanding the collective migration of cells, such as that seen in epithelial sheets, is essential for understanding diseases such as metastatic cancer, this motion is not yet as well characterized as individual cell migration. Here we adapt quantitative metrics used to characterize the flow and deformation of soft matter to contrast different types of motion within a migrating sheet of cells. Using a Finite-Time Lyapunov Exponent (FTLE) analysis, we find that - in spite of large fluctuations - the flow field of an epithelial cell sheet is not chaotic. Stretching of a sheet of cells (i.e., positive FTLE) is localized at the leading edge of migration and increases when the cells are more highly stimulated. By decomposing the motion of the cells into affine and non-affine components using the metric D(2)min , we quantify local plastic rearrangements and describe the motion of a group of cells in a novel way. We find an increase in plastic rearrangements with increasing cell densities, whereas inanimate systems tend to exhibit less non-affine rearrangements with increasing density.

  19. Rapid identification of chromosomal rearrangements by PRINS technique

    SciTech Connect

    Pellestor, F.; Giradet, A.; Andreo, B.

    1994-09-01

    Chromosomal rearrangements contribute significantly to human reproductive failure, malformation/mental retardation syndromes and carcinogenesis. The variety of structural rearrangements is almost infinite and an identification by conventional cytogenetics is often labor intensive and may remain doubtful. Recent advances in molecular cytogenetics have provided new tools for detecting chromosomal abnormalities. The fluorescence in situ hybridization (FISH) procedure is actually the most employed technique and has led to numerous clinical applications. However, techniques required to produce suitable probes are time consuming and not accessible to all cytogenetics laboratories. The PRimed In Situ labeling (PRINS) method provides an alternate way for in situ chromosome screening. In this procedure, the chromosomal detection is performed by in situ annealing of a specific primer and subsequent primer extension by a Taq DNA polymerase in the presence of labeled nucleotides. Application of PRINS in clinical diagnosis is still limited. We have developed a semi-automatic PRINS protocol and used it to identify the origin of several chromosomal abnormalities. We report here the results of studies of three structural rearrangements: a translocation t(21;21), a supernumerary ring marker chromosome 18 and a complex chromosome 13 mosaicism involving a 13;13 Robertsonian translocation and a ring chromosome 13.

  20. Elevated Rate of Genome Rearrangements in Radiation-Resistant Bacteria

    PubMed Central

    Repar, Jelena; Supek, Fran; Klanjscek, Tin; Warnecke, Tobias; Zahradka, Ksenija; Zahradka, Davor

    2017-01-01

    A number of bacterial, archaeal, and eukaryotic species are known for their resistance to ionizing radiation. One of the challenges these species face is a potent environmental source of DNA double-strand breaks, potential drivers of genome structure evolution. Efficient and accurate DNA double-strand break repair systems have been demonstrated in several unrelated radiation-resistant species and are putative adaptations to the DNA damaging environment. Such adaptations are expected to compensate for the genome-destabilizing effect of environmental DNA damage and may be expected to result in a more conserved gene order in radiation-resistant species. However, here we show that rates of genome rearrangements, measured as loss of gene order conservation with time, are higher in radiation-resistant species in multiple, phylogenetically independent groups of bacteria. Comparison of indicators of selection for genome organization between radiation-resistant and phylogenetically matched, nonresistant species argues against tolerance to disruption of genome structure as a strategy for radiation resistance. Interestingly, an important mechanism affecting genome rearrangements in prokaryotes, the symmetrical inversions around the origin of DNA replication, shapes genome structure of both radiation-resistant and nonresistant species. In conclusion, the opposing effects of environmental DNA damage and DNA repair result in elevated rates of genome rearrangements in radiation-resistant bacteria. PMID:28188144

  1. Engineering the Drosophila Genome: Chromosome Rearrangements by Design

    PubMed Central

    Golic, K. G.; Golic, M. M.

    1996-01-01

    We show that site-specific recombination can be used to engineer chromosome rearrangements in Drosophila melanogaster. The FLP site-specific recombinase acts on chromosomal target sites located within specially constructed P elements to provide an easy screen for the recovery of rearrangements with breakpoints that can be chosen in advance. Paracentric and pericentric inversions are easily recovered when two elements lie in the same chromosome in opposite orientation. These inversions are readily reversible. Duplications and deficiencies can be recovered by recombination between two elements that lie in the same orientation on the same chromosome or on homologues. We observe that the frequency of recombination between FRTs at ectopic locations decreases as the distance that separates those FRTs increases. We also describe methods to determine the absolute orientation of these P elements within the chromosome. The ability to produce chromosome rearrangements precisely between preselected sites provides a powerful new tool for investigations into the relationships between chromosome arrangement, structure, and function. PMID:8978056

  2. Extended Rearrangement Inequalities and Applications to Some Quantitative Stability Results

    NASA Astrophysics Data System (ADS)

    Lemou, Mohammed

    2016-12-01

    In this paper, we prove a new functional inequality of Hardy-Littlewood type for generalized rearrangements of functions. We then show how this inequality provides quantitative stability results of steady states to evolution systems that essentially preserve the rearrangements and some suitable energy functional, under minimal regularity assumptions on the perturbations. In particular, this inequality yields a quantitative stability result of a large class of steady state solutions to the Vlasov-Poisson systems, and more precisely we derive a quantitative control of the L 1 norm of the perturbation by the relative Hamiltonian (the energy functional) and rearrangements. A general non linear stability result has been obtained by Lemou et al. (Invent Math 187:145-194, 2012) in the gravitational context, however the proof relied in a crucial way on compactness arguments which by construction provides no quantitative control of the perturbation. Our functional inequality is also applied to the context of 2D-Euler systems and also provides quantitative stability results of a large class of steady-states to this system in a natural energy space.

  3. Metalla-cope rearrangements: bridging organic and inorganic chemistry.

    PubMed

    Greer, Edyta M; Hoffmann, Roald

    2010-08-26

    Density functional theory calculations are performed to explore both concerted chairlike and boatlike as well as stepwise mechanisms of the Cope rearrangement of two hypothetical metalladienes. An osma-1,5-hexadiene is designed by substituting CH(2) in 1,5-hexadiene by its isolobal analogue, 16-electron Os(PH(3))(4). The energy of activation corresponding to the rearrangement of osma-1,5-hexadiene involving the chairlike saddle point is computed as 37.4 kcal/mol, 3.9 kcal/mol above the energy barrier of the parent 1,5-hexadiene calculated with the same method and basis set, and is 4.5 kcal/mol below that of the boatlike pathway. In another isolobal replacement, the CH in 1,5-hexadiene is substituted by a 15-electron Re(PH(3))(3) fragment. Now the chairlike rearrangement of the rhenia-1,5-hexadiene has an E(a) value of 23.0 kcal/mol, 10.8 kcal/mol less than the energy barrier of the parent 1,5-hexadiene calculated at the same level of theory. The ring inversion of the chair and osma-chair diradical intermediates of the stepwise reaction pathway is also examined and is found in both cases to proceed through a very flat potential energy surface involving twist intermediates.

  4. Photo-induced and electrooptic properties of (Pb,La)(Zr,Ti) O{sub 3} films for optical memories

    SciTech Connect

    Dimos, D.; Potter, B.G.; Sinclair, M.B.; Tuttle, B.A.; Warren, W.L.

    1993-09-01

    Photo-induced hysteresis changes and electrooptic effects in sol-gel Pb(Zr,Ti)0{sub 3} (PZT) and PLZT films have been studied in an effort to evaluate these materials for optical memory applications. The films exhibit two types of photo-induced changes in their hysteresis behavior which are suitable for optical storage. Both types of photo-induced hysteresis changes are due to trapping of photo-generated charge carriers at sites which minimize internal depolarizing fields. The photo-induced changes are reproducible and stable, which indicates that the charge traps are stable. However, improvements in photosensitivity will be required to develop a competitive technology for optical memories. In addition, polarization-dependent changes in the refractive indices can be the basis of a nondestructive optical readout technique. The index changes of films have been determined using a waveguide refractometry technique, which allows the extraordinary and ordinary index changes to be obtained independently.

  5. Photoinduced modulation and relaxation characteristics in LaAlO3/SrTiO3 heterointerface

    PubMed Central

    Jin, K. X.; Lin, W.; Luo, B. C.; Wu, T.

    2015-01-01

    We report the modulation and relaxation characteristics in the two-dimensional electron gas system at LaAlO3/SrTiO3 heterointerface induced by the ultraviolet light illumination (365 nm). The suppression of Kondo effect at the interface illuminated by the light originates from the light irradiation-induced decoherence effect of localized states. It is interesting to note that the persistent and transient photoinduced effects are simultaneously observed and the photoinduced maximum change values in resistance are 80.8% and 51.4% at T = 20 K, respectively. Moreover, the photoinduced relaxation processes after the irradiation are systematically analyzed using the double exponential model. These results provide the deeper understanding of the photoinduced effect and the experimental evidence of tunable Kondo effect in oxides-based two-dimensional electron gas systems. PMID:25739889

  6. Photo-induced and electrooptic properties of (Pb,La)(Zr,Ti)O3 films for optical memories

    NASA Astrophysics Data System (ADS)

    Dimos, D.; Potter, B. G.; Sinclair, M. B.; Tuttle, B. A.; Warren, W. L.

    Photo-induced hysteresis changes and electro-optic effects in sol-gel Pb(Zr,Ti)03 (PZT) and PLZT films have been studied in an effort to evaluate these materials for optical memory applications. The films exhibit two types of photo-induced changes in their hysteresis behavior which are suitable for optical storage. Both types of photo-induced hysteresis changes are due to trapping of photo-generated charge carriers at sites which minimize internal depolarizing fields. The photo-induced changes are reproducible and stable, which indicates that the charge traps are stable. However, improvements in photosensitivity will be required to develop a competitive technology for optical memories. In addition, polarization-dependent changes in the refractive indices can be the basis of a nondestructive optical readout technique. The index changes of films have been determined using a waveguide refractometry technique, which allows the extraordinary and ordinary index changes to be obtained independently.

  7. Photo-induced current amplification in L-histidine modified nanochannels based on a highly charged photoacid in solution.

    PubMed

    Zhang, Minghui; Meng, Zheyi; Zhai, Jin; Jiang, Lei

    2013-03-21

    By UV light irradiation, we can adjust the charge of bistable photoacid molecules reversibly, so that photo-induced current amplification can be obtained, which offers a way to control nanochannels by turning the UV light on and off, alternately.

  8. Photoinduced electron transfer reaction in polymer-surfactant aggregates: Photoinduced electron transfer between N,N-dimethylaniline and 7-amino coumarin dyes

    SciTech Connect

    Chakraborty, Anjan; Seth, Debabrata; Setua, Palash; Sarkar, Nilmoni

    2008-05-28

    Photoinduced electron transfer between coumarin dyes and N,N-dimethylaniline has been investigated by using steady state and picosecond time resolved fluorescence spectroscopy in sodium dodecyl sulphate (SDS) micelles and PVP-polyvinyl pyrrolidone (SDS) polymer-surfactant aggregates. A slower rate of electron transfer is observed in PVP-SDS aggregates than in polymer-free SDS micelles. A Marcus type inversion is observed in the correlation of free energy change in comparison with the electron transfer rate. The careful investigation reveals that C-151 deviates from the normal Marcus inverted region compared to its analogs C-152 and C-481 due to slower rotational relaxation and smaller translational diffusion coefficient.

  9. Acute photo-induced toxicity and toxicokinetics of single compounds and mixtures of polycyclic aromatic hydrocarbons in zebrafish.

    PubMed

    Willis, Alison M; Oris, James T

    2014-09-01

    The present study examined photo-induced toxicity and toxicokinetics for acute exposure to selected polycyclic aromatic hydrocarbons (PAHs) in zebrafish. Photo-enhanced toxicity from co-exposure to ultraviolet (UV) radiation and PAHs enhanced the toxicity and exhibited toxic effects at PAH concentrations orders of magnitude below effects observed in the absence of UV. Because environmental exposure to PAHs is usually in the form of complex mixtures, the present study examined the photo-induced toxicity of both single compounds and mixtures of PAHs. In a sensitive larval life stage of zebrafish, acute photo-induced median lethal concentrations (LC50s) were derived for 4 PAHs (anthracene, pyrene, carbazole, and phenanthrene) to examine the hypothesis that phototoxic (anthracene and pyrene) and nonphototoxic (carbazole and phenanthrene) pathways of mixtures could be predicted from single exposures. Anthracene and pyrene were phototoxic as predicted; however, carbazole exhibited moderate photo-induced toxicity and phenanthrene exhibited weak photo-induced toxicity. The toxicity of each chemical alone was used to compare the toxicity of mixtures in binary, tertiary, and quaternary combinations of these PAHs, and a predictive model for environmental mixtures was generated. The results indicated that the acute toxicity of PAH mixtures was additive in phototoxic scenarios, regardless of the magnitude of photo-enhancement. Based on PAH concentrations found in water and circumstances of high UV dose to aquatic systems, there exists potential risk of photo-induced toxicity to aquatic organisms.

  10. Reply to comment by E. W. Wolff et al. on "Low time resolution analysis of polar ice cores cannot detect impulsive nitrate events"

    NASA Astrophysics Data System (ADS)

    Smart, D. F.; Shea, M. A.; Melott, A. L.; Laird, C. M.

    2016-03-01

    Wolff et al. (2016) comment on Smart et al. (2014) and in doing so concentrate on issues other than the main point. They do not dispute our central assertion, the inadequate resolution of nearly all extant ice cores for detection of impulsive nitrate events (spikes) from any source, including past solar proton events (SPEs). We explain why comparing two short-length cores from other researchers and analyzed by different methods is insufficient for disputing subannual reproducibility, and call for a multiple, fine-resolution, replicate core study to resolve this issue. While acknowledging the creation of nitrate by SPEs and the existence of ice core nitrate spikes detected by others, they present several weak arguments, such as alleged scavenging of nitrate by some unnamed and unmeasured aerosol, and why no enhanced nitrate signal for documenting SPE statistics should be distinguishable in the ice. These are not derived from the main points in our Smart et al. (2014) paper. We address these briefly and show that ionization from the February 1956 SPE was sufficient to produce a winter, likely acidic, nitrate spike at Summit, Greenland. While noting some convergence of interpretation, we show why their claim that nitrate spikes cannot be used for deriving SPE statistics is unproven and why rejection of fine resolution core studies as unreliable is premature.

  11. [Outcome of Wolff-Parkinson-White syndrome in children. Transesophageal study of anterograde permeability of the accessory pathway and of atrial vulnerability].

    PubMed

    Villain, E; Attali, T; Iserin, L; Aggoun, Y; Kachaner, J

    1994-05-01

    Twenty-nine children with the Wolff-Parkinson-White syndrome (WPW) were evaluated by transoesophageal electrophysiological studies to determine the quality of anterograde-conduction in the accessory pathway and the atrial vulnerability. The study group included 15 neonates, 1 to 30 days old, and 14 children from 5 to 15 years of age; Anterograde conduction through the bundle of Kent was tested by incremental transoesophageal atrial pacing and by the determination of the shortest conducted cycle with preexcited RR waves; bursts of atrial pacing were then used to try to trigger an atrial arrhythmia. In the group of the 15 neonates, 11 had accessory pathways capable of conduction to the ventricules at frequencies > 300/min (stimulation cycle < or = 2.00 ms) but no atrial arrhythmias could be induced. The older children had slower conduction in the accessory pathways with the shortest conducted cycle length > 200 ms in 11/14 cases; on the other hand, atrial fibrillation was easily induced in 4 children, all over 12 years of age. The risk of syncope by rapid conduction of an atrial arrhythmia through the accessory pathway is negligeable in young children, including those on digoxin. This study suggests that this low risk is explained more by the absence of atrial vulnerability than by the electrophysiological properties of the accessory pathways.

  12. A bifunctional amorphous polymer exhibiting equal linear and circular photoinduced birefringences.

    PubMed

    Royes, Jorge; Provenzano, Clementina; Pagliusi, Pasquale; Tejedor, Rosa M; Piñol, Milagros; Oriol, Luis

    2014-11-01

    The large and reversible photoinduced linear and circular birefringences in azo-compounds are at the basis of the interest in these materials, which are potentially useful for several applications. Since the onset of the linear and circular anisotropies relies on orientational processes, which typically occur on the molecular and supramolecular length scale, respectively, a circular birefringence at least one order of magnitude lower than the linear one is usually observed. Here, the synthesis and characterization of an amorphous polymer with a dimeric repeating unit containing a cyanoazobenzene and a cyanobiphenyl moiety are reported, in which identical optical linear and circular birefringences are induced for proper light dose and ellipticity. A pump-probe technique and an analytical method based on the Stokes-Mueller formalism are used to investigate the photoinduced effects and to evaluate the anisotropies. The peculiar photoresponse of the polymer makes it a good candidate for applications in smart functional devices.

  13. Enhanced diffraction properties of photoinduced gratings in nematic liquid crystals doped with Disperse Red 1.

    PubMed

    Li, Hongjing; Wang, Jianhao; Wang, Changshun; Zeng, Pengfei; Pan, Yujia; Yang, Yifei

    2016-01-01

    Diffraction properties of photoinduced gratings recorded by overlapping two coherent beams at 532 nm in nematic liquid crystals doped with Disperse Red 1 were investigated with a probe beam at 632.8 nm. The grating was formed due to the alignment of dye molecules that leaded to the reorientation of the liquid crystal phase. The diffraction efficiency of the photoinduced grating was found to increase rapidly when the sample temperature was close to the clearing point in the nematic phase and a nearly 30-fold enhancement of the first-order diffraction efficiency was obtained. The pretransitional enhancement of the diffraction efficiency was discussed in terms of the reorientation of liquid crystals, optical nonlinearity effects and the onset of critical opalescence near the nematic-isotropic phase transition. Moreover, a peak shift of diffraction efficiency towards the lower temperature was observed with the increase of recording light intensity, which was attributed to laser induced photochemical disordering.

  14. Genetically engineered photoinducible homodimerization system with improved dimer-forming efficiency.

    PubMed

    Nihongaki, Yuta; Suzuki, Hideyuki; Kawano, Fuun; Sato, Moritoshi

    2014-03-21

    Vivid (VVD) is a photoreceptor derived from Neurospora Crassa that rapidly forms a homodimer in response to blue light. Although VVD has several advantages over other photoreceptors as photoinducible homodimerization system, VVD has a critical limitation in its low dimer-forming efficiency. To overcome this limitation of wild-type VVD, here we conduct site-directed saturation mutagenesis in the homodimer interface of VVD. We have found that the Ile52Cys mutation of VVD (VVD-52C) substantially improves its homodimer-forming efficiency up to 180%. We have demonstrated the utility of VVD-52C for making a light-inducible gene expression system more robust. In addition, using VVD-52C, we have developed photoactivatable caspase-9, which enables optical control of apoptosis of mammalian cells. The present genetically engineered photoinducible homodimerization system can provide a powerful tool to optically control a broad range of molecular processes in the cell.

  15. Enhanced diffraction properties of photoinduced gratings in nematic liquid crystals doped with Disperse Red 1

    PubMed Central

    LI, Hongjing; WANG, Jianhao; WANG, Changshun; ZENG, Pengfei; PAN, Yujia; YANG, Yifei

    2016-01-01

    Diffraction properties of photoinduced gratings recorded by overlapping two coherent beams at 532 nm in nematic liquid crystals doped with Disperse Red 1 were investigated with a probe beam at 632.8 nm. The grating was formed due to the alignment of dye molecules that leaded to the reorientation of the liquid crystal phase. The diffraction efficiency of the photoinduced grating was found to increase rapidly when the sample temperature was close to the clearing point in the nematic phase and a nearly 30-fold enhancement of the first-order diffraction efficiency was obtained. The pretransitional enhancement of the diffraction efficiency was discussed in terms of the reorientation of liquid crystals, optical nonlinearity effects and the onset of critical opalescence near the nematic-isotropic phase transition. Moreover, a peak shift of diffraction efficiency towards the lower temperature was observed with the increase of recording light intensity, which was attributed to laser induced photochemical disordering. PMID:27725471

  16. Photo-induced Modulation Doping in Graphene/Boron nitride Heterostructures

    NASA Astrophysics Data System (ADS)

    Velasco, Jairo, Jr.; Ju, Long; Hwang, Edwin; Kahn, Salman; Nosiglia, Casey; Tsai, Hsin-Zon; Yang, Wei; Zhang, Guangyu; Taniguchi, Takashi; Watanabe, Kenji; Zhang, Yuanbo; Crommie, Michael; Zettl, Alex; Wang, Feng

    2014-03-01

    Van der Waals heterostructures (VDH) provide an exciting new platform for materials engineering, where a variety of layered materials with different electrical, optical and mechanical responses can be stacked together to enable new physics and novel functionalities. We report an emerging optoelectronic phenomenon (i.e. photo-induced modulation doping) in the graphene-boron nitride VDH (G/BN heterostructure). We find it enables flexible and repeatable writing and erasing of charge doping in graphene with optical light. We show that the photo-induced modulation doping maintains the remarkable carrier mobility of the G/BN heterostructure, and it can be used to generate spatially varying doping profiles like pn junctions. Our work contributes towards understanding light matter interactions in VDHs, and introduces a simple technique for creating inhomogeneous doping in high mobility graphene devices. J. Velasco Jr. acknowledges support from UC President's Postdoctoral Fellowship.

  17. Eigenmodes of a quartz tuning fork and their application to photoinduced force microscopy

    NASA Astrophysics Data System (ADS)

    Kim, Bongsu; Jahng, Junghoon; Khan, Ryan Muhammad; Park, Sung; Potma, Eric O.

    2017-02-01

    We examine the mechanical eigenmodes of a quartz tuning fork (QTF) for the purpose of facilitating its use as a probe for multifrequency atomic force microscopy (AFM). We perform simulations based on the three-dimensional finite element method and compare the observed motions of the beams with experimentally measured resonance frequencies of two QTF systems. The comparison enabled us to assign the first seven asymmetric eigenmodes of the QTF. We also find that a modified version of single beam theory can be used to guide the assignment of mechanical eigenmodes of QTFs. The usefulness of the QTF for multifrequency AFM measurements is demonstrated through photoinduced force microscopy measurements. By using the QTF in different configurations, we show that the vectorial components of the photoinduced force can be independently assessed and that lateral forces can be probed in true noncontact mode.

  18. Photo-induced changes in a hybrid amorphous chalcogenide/silica photonic crystal fiber

    SciTech Connect

    Markos, Christos

    2014-01-06

    Photostructural changes in a hybrid photonic crystal fiber with chalcogenide nanofilms inside the inner surface of the cladding holes are experimentally demonstrated. The deposition of the amorphous chalcogenide glass films inside the silica capillaries of the fiber was made by infiltrating the nanocolloidal solution-based As{sub 25}S{sub 75}, while the photoinduced changes were performed by side illuminating the fiber near the bandgap edge of the formed glass nanofilms. The photoinduced effect of the chalcogenide glass directly red-shifts the transmission bandgap position of the fiber as high as ∼20.6 nm at around 1600 nm wavelength, while the maximum bandgap intensity change at ∼1270 nm was −3 dB.

  19. A dinuclear Ru(II) complex capable of photoinduced ligand exchange at both metal centers.

    PubMed

    Albani, B A; Peña, B; Saha, S; White, J K; Schaeffer, A M; Dunbar, K R; Turro, C

    2015-11-28

    {[Ru(CH3CN)3]2(tppz)}(4+) (tppz = tetra-2-pyridylpyrazine) undergoes photoinduced CH3CN exchange with λirr ≥ 610 nm in H2O. In contrast, cis-{[Ru(tpy)(L)]2(bpm)}(4+) (tpy = 2,2':6',2''-terpyridine, bpm = 2,2'-bipyrimidine, L = CH3CN) is not reactive, but the complex with L = DMSO is photoactive. These complexes are potentially useful for the release of multiply caged drugs.

  20. Stochastic model for photoinduced surface relief grating formation through molecular transport in polymer films.

    SciTech Connect

    Juan, M.; Plain, J.; Bachelot, R.; Royer, P.; Gray, S. K.; Wiederrecht, G. P.; Univ. de Technologie de Troyes

    2008-09-01

    We use a stochastic model to study photoinduced surface relief grating (SRG) formation due to molecular transport in azobenzene polymer films. The model is shown to reproduce the essential experimental features of SRG formation. In particular, it predicts SRG formation under both p and s polarizations, and the double peaked topographies that can occur at early times of the process. The evolving molecular positions and orientations during exposure are also followed, providing a useful mechanistic picture of SRG dynamics.

  1. Stochastic model for photoinduced surface relief grating formation through molecular transport in polymer films

    SciTech Connect

    Juan, M. L.; Plain, J.; Bachelot, R.; Royer, P.; Gray, S. K.; Wiederrecht, G. P.

    2008-10-13

    We use a stochastic model to study photoinduced surface relief grating (SRG) formation due to molecular transport in azobenzene polymer films. The model is shown to reproduce the essential experimental features of SRG formation. In particular, it predicts SRG formation under both p and s polarizations, and the double peaked topographies that can occur at early times of the process. The evolving molecular positions and orientations during exposure are also followed, providing a useful mechanistic picture of SRG dynamics.

  2. Procedure for quantitative determination of effectiveness of photoinduced destruction of malignant tumors

    NASA Astrophysics Data System (ADS)

    Bizyuk, S. A.; Istomin, Yu. P.; Dzhagarov, B. M.

    2006-07-01

    We have developed a procedure for analysis of the functional status of blood vessels in tumor tissues using computer-assisted color scanning of tumor slices and also for a quantitative assessment of the effectiveness of photoinduced destruction of tumor tissues in animal experiments. Its major advantage is direct determination of the size of the tumor necrosis zone. The procedure has been tested in an experiment on three strains of malignant tumors with different morphologies.

  3. Monte-Carlo simulations of photoinduced fluorescence enhancement in semiconductor quantum dot arrays

    NASA Astrophysics Data System (ADS)

    Maenosono, Shinya

    2005-03-01

    Photoinduced fluorescence enhancement (PFE) in semiconductor quantum dot (QD) arrays is simulated by a Monte-Carlo method based on the distributed tunneling model. PFE, a property of a QD ensemble, is directly related to the blinking behavior of single QDs. The origin of PFE is attributed not to an increase in the emission intensity during the 'on' period, but to the prolongation of average 'on' time.

  4. Photoinduced changes in refractive index of nanostructured shungite-containing polyimide systems

    NASA Astrophysics Data System (ADS)

    Kamanina, N. V.; Serov, S. V.; Shurpo, N. A.; Rozhkova, N. N.

    2011-10-01

    Photoinduced changes in the refractive index of a conjugate polyimide (PI) matrix sensitized by shungite carbon nanoparticles have been studied for the first time. The results are compared to the data of previous investigations of the photorefractive properties of PI matrices doped with fullerenes, carbon nanotubes, and quantum dots. The nonlinear refractive index of the proposed material has been determined using the dynamic holography techniques. The position of conjugate polymer materials of this type among the other nonlinear optical systems is considered.

  5. Time-Resolved Studies of Photoinduced Birefringence in Azobenzene Dye-Doped Polymer Films

    DTIC Science & Technology

    2008-09-23

    Here we report on transient photoinduced birefrin- gence ( PIB ) measurements on several azo dye films using a nanosecond laser source with a 20ns time re...Our results show the response time of PIB to be sys- tematically related to the size of the lowest optical transition energy. Furthermore, our results...suggest that PIB effects can be used to discriminate between0003-6935/08/285074-04$15.00/0 © 2008 Optical Society of America 5074 APPLIED OPTICS / Vol

  6. Electron Donor-Acceptor Quenching and Photoinduced Electron Transfer for Coumarin Dyes.

    DTIC Science & Technology

    1983-10-31

    Mechanism of cousarin photodegradation . Ithe behavior of eoiuma dyes is water ad In aqueous detergent media,. and the effsects of medism aud, additives on...D-i36 345 ELECTRON DONOR-ACCEPTOR UENCHING AND PHOTOINDUCED i/i Ai ELECTRON TRANSFER FOR COUMARIN DYES (U) BOSTON UNIY MR DEPT OF CHEMISTRY G JONES...TYPE OF REPORT & PEIOD COVERED Electron Donor-acceptor Quenching and Photo- Technical, 1/1/82-10/31/82 induced Electron Transfer for Coumarin Dyes S

  7. 8-Methoxypsoralen photoinduced plasmid-chromosome recombination in Saccharomyces cerevisiae using a centromeric vector.

    PubMed Central

    Meira, L B; Henriques, J A; Magaña-Schwencke, N

    1995-01-01

    The characterization of a new system to study the induction of plasmid-chromosome recombination is described. Single-stranded and double-stranded centromeric vectors bearing 8-methoxypsoralen photoinduced lesions were used to transform a wild-type yeast strain bearing the leu2-3,112 marker. Using the SSCP methodology and DNA sequencing, it was demonstrated that repair of the lesions in plasmid DNA was mainly due to conversion of the chromosomal allele to the plasmid DNA. Images PMID:7784218

  8. Mitochondrial DNA Rearrangement Spectrum in Brain Tissue of Alzheimer’s Disease: Analysis of 13 Cases

    PubMed Central

    Chen, Yucai; Liu, Changsheng; Parker, William Davis; Chen, Hongyi; Beach, Thomas G.; Liu, Xinhua; Serrano, Geidy E.; Lu, Yanfen; Huang, Jianjun; Yang, Kunfang; Wang, Chunmei

    2016-01-01

    Background Mitochondrial dysfunction may play a central role in the pathologic process of Alzheimer’s disease (AD), but there is still a scarcity of data that directly links the pathology of AD with the alteration of mitochondrial DNA. This study aimed to provide a comprehensive assessment of mtDNA rearrangement events in AD brain tissue. Patients and Methods Postmortem frozen human brain cerebral cortex samples were obtained from the Banner Sun Health Research Institute Brain and Body Donation Program, Sun City, AZ. Mitochondria were isolated and direct sequence by using MiSeq®, and analyzed by relative software. Results Three types of mitochondrial DNA (mtDNA) rearrangements have been seen in post mortem human brain tissue from patients with AD and age matched control. These observed rearrangements include a deletion, F-type rearrangement, and R-type rearrangement. We detected a high level of mtDNA rearrangement in brain tissue from cognitively normal subjects, as well as the patients with Alzheimer's disease (AD). The rate of rearrangements was calculated by dividing the number of positive rearrangements by the coverage depth. The rearrangement rate was significantly higher in AD brain tissue than in control brain tissue (17.9%versus 6.7%; p = 0.0052). Of specific types of rearrangement, deletions were markedly increased in AD (9.2% versus 2.3%; p = 0.0005). Conclusions Our data showed that failure of mitochondrial DNA in AD brain might be important etiology of AD pathology. PMID:27299301

  9. Neuronal regulation of photo-induced pineal photoreceptor proteins in carp Catla catla.

    PubMed

    Seth, Mohua; Maitra, Saumen Kumar

    2010-08-01

    In the present in vitro study on the pineal in carp Catla catla, specific agonist and antagonists of receptors for different neuronal signals and regulators of intra-cellular Ca(++) and cAMP were used to gather basic information on the neuronal signal transduction cascade mechanisms in the photo-induced expression of rod-like opsin and alpha-transducin-like proteins in any fish pineal. Western-blot analysis followed by quantitative analysis of respective immunoblot data for both the proteins revealed that photo-induced expression of each protein was stimulated by cholinergic (both nicotinic and muscarinic) agonists and a dopaminergic antagonist, inhibited by both cholinergic antagonists and a dopaminergic agonist, but not affected by any agonists or antagonists of adrenergic (alpha(1), alpha(2) and beta(1)) receptors. Moreover, expression of each protein was stimulated by voltage gated L type calcium channel blocker, adenylate cyclase inhibitor and phosphodiesterase activator; but suppressed by the activators of both calcium channel and adenylate cyclase, and by phosphodiesterase inhibitor. Collectively, we report for the first time that both cholinergic and dopaminergic signals play an important, though antagonistic, role in the photo-induced expression of photoreceptor proteins in the fish pineal through activation of a signal transduction pathway in which both calcium and cAMP may act as the intracellular messengers.

  10. The nature of photoinduced phase transition and metastable states in vanadium dioxide

    PubMed Central

    Tao, Zhensheng; Zhou, Faran; Han, Tzong-Ru T.; Torres, David; Wang, Tongyu; Sepulveda, Nelson; Chang, Kiseok; Young, Margaret; Lunt, Richard R.; Ruan, Chong-Yu

    2016-01-01

    Photoinduced threshold switching processes that lead to bistability and the formation of metastable phases in photoinduced phase transition of VO2 are elucidated through ultrafast electron diffraction and diffusive scattering techniques with varying excitation wavelengths. We uncover two distinct regimes of the dynamical phase change: a nearly instantaneous crossover into an intermediate state and its decay led by lattice instabilities over 10 ps timescales. The structure of this intermediate state is identified to be monoclinic, but more akin to M2 rather than M1 based on structure refinements. The extinction of all major monoclinic features within just a few picoseconds at the above-threshold-level (~20%) photoexcitations and the distinct dynamics in diffusive scattering that represents medium-range atomic fluctuations at two photon wavelengths strongly suggest a density-driven and nonthermal pathway for the initial process of the photoinduced phase transition. These results highlight the critical roles of electron correlations and lattice instabilities in driving and controlling phase transformations far from equilibrium. PMID:27982066

  11. The nature of photoinduced phase transition and metastable states in vanadium dioxide

    NASA Astrophysics Data System (ADS)

    Tao, Zhensheng; Zhou, Faran; Han, Tzong-Ru T.; Torres, David; Wang, Tongyu; Sepulveda, Nelson; Chang, Kiseok; Young, Margaret; Lunt, Richard R.; Ruan, Chong-Yu

    2016-12-01

    Photoinduced threshold switching processes that lead to bistability and the formation of metastable phases in photoinduced phase transition of VO2 are elucidated through ultrafast electron diffraction and diffusive scattering techniques with varying excitation wavelengths. We uncover two distinct regimes of the dynamical phase change: a nearly instantaneous crossover into an intermediate state and its decay led by lattice instabilities over 10 ps timescales. The structure of this intermediate state is identified to be monoclinic, but more akin to M2 rather than M1 based on structure refinements. The extinction of all major monoclinic features within just a few picoseconds at the above-threshold-level (~20%) photoexcitations and the distinct dynamics in diffusive scattering that represents medium-range atomic fluctuations at two photon wavelengths strongly suggest a density-driven and nonthermal pathway for the initial process of the photoinduced phase transition. These results highlight the critical roles of electron correlations and lattice instabilities in driving and controlling phase transformations far from equilibrium.

  12. Highly active ppm level organic copper catalyzed photo-induced ICAR ATRP of methyl methacrylate.

    PubMed

    Jiang, Xiaowu; Wu, Jian; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

    2014-11-01

    A novel photo-induced homogeneous atom transfer radical polymerization (ATRP) system is constructed using an organic copper salt (Cu(SC(S)N(C2 H5 )2 )2 ) as a photo-induced catalyst at 30 °C. Herein, N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) is used as a ligand, ethyl 2-bromophenylacetate (EBPA) as an ATRP initiator, and (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TPO) as a photo-induced radical initiator to establish an ICAR (initiators for continuous activator regeneration) ATRP using methyl methacrylate (MMA) as a modal monomer. The effect of the concentration of the organic copper on the polymerization is investigated in detail. It is found that well-controlled polymerization can be obtained even with the amount of (Cu(SC(S)N(C2 H5 )2 )2 decreasing to a 1.56 ppm level, with the molecular weight of the resultant polymers increasing linearly with monomer conversion while maintaining a narrow molecular weight distribution (M¯w/M¯n < 1.3).

  13. Photoinduced Oxidative DNA Damage Revealed by an Agarose Gel Nicking Assay: A Biophysical Chemistry Laboratory Experiment

    NASA Astrophysics Data System (ADS)

    Shafirovich, Vladimir; Singh, Carolyn; Geacintov, Nicholas E.

    2003-11-01

    Oxidative damage of DNA molecules associated with electron-transfer reactions is an important phenomenon in living cells, which can lead to mutations and contribute to carcinogenesis and the aging processes. This article describes the design of several simple experiments to explore DNA damage initiated by photoinduced electron-transfer reactions sensitized by the acridine derivative, proflavine (PF). A supercoiled DNA agarose gel nicking assay is employed as a sensitive probe of DNA strand cleavage. A low-cost experimental and computer-interfaced imaging apparatus is described allowing for the digital recording and analysis of the gel electrophoresis results. The first experiment describes the formation of direct strand breaks in double-stranded DNA induced by photoexcitation of the intercalated PF molecules. The second experiment demonstrates that the addition of the well-known electron acceptor, methylviologen, gives rise to a significant enhancement of the photochemical DNA strand cleavage effect. This occurs by an electron transfer step to methylviologen that renders the inital photoinduced charge separation between photoexcited PF and DNA irreversible. The third experiment demonstrates that the action spectrum of the DNA photocleavage matches the absorption spectrum of DNA-bound, intercalated PF molecules, which differs from that of free PF molecules. This result demonstrates that the photoinduced DNA strand cleavage is initiated by intercalated rather than free PF molecules.

  14. The photoinduced dynamics of X[M(dmit)2]2 salts

    NASA Astrophysics Data System (ADS)

    Ishikawa, Tadahiko; Hayes, Stuart A.; Miller, R. J. Dwayne; Hada, Masaki; Koshihara, Shinya

    2017-03-01

    We review our work on the photoinduced dynamics of X[M(dmit)2]2 salts in the charge-separated (CS) phase from the viewpoints of both electronic structural change and lattice or molecular structural change. The driving force for the CS phase formation is a strong correlation among the charge distribution, orbital energies, and the molecular structure; this is in contrast to frequently studied charge-ordered systems such as EDOTTF2PF6, whose formation is mainly driven by the intersite Coulomb repulsion. Despite the localized nature of the structural component, the cooperativity inherent to the crystal is likely to play an important role in photoinduced phenomena. In this review, we summarize the results obtained by a series of optical pump-probe experiments on this class of materials. We have also recently extended these studies using ultrafast electron diffraction to follow the nuclear motion in one of these systems. Such information is crucial for a full understanding of the photoinduced phenomena and it is anticipated that combining the results of the optical and diffraction studies will lead to more fruitful insight than either technique can offer in isolation.

  15. Phase diagram of the ultrafast photoinduced insulator-metal transition in vanadium dioxide

    NASA Astrophysics Data System (ADS)

    Cocker, T. L.; Titova, L. V.; Fourmaux, S.; Holloway, G.; Bandulet, H.-C.; Brassard, D.; Kieffer, J.-C.; El Khakani, M. A.; Hegmann, F. A.

    2012-04-01

    We use time-resolved terahertz spectroscopy to probe the ultrafast dynamics of the insulator-metal phase transition induced by femtosecond laser pulses in a nanogranular vanadium dioxide (VO2) film. Based on the observed thresholds for characteristic transient terahertz dynamics, a phase diagram of critical pump fluence versus temperature for the insulator-metal phase transition in VO2 is established for the first time over a broad range of temperatures down to 17 K. We find that both Mott and Peierls mechanisms are present in the insulating state and that the photoinduced transition is nonthermal. We propose a critical-threshold model for the ultrafast photoinduced transition based on a critical density of electrons and a critical density of coherently excited phonons necessary for the structural transition to the metallic state. As a result, evidence is found at low temperatures for an intermediate metallic state wherein the Mott state is melted but the Peierls distortion remains intact, consistent with recent theoretical predictions. Finally, the observed terahertz conductivity dynamics above the photoinduced transition threshold reveal nucleation and growth of metallic nanodomains over picosecond time scales.

  16. Photo-induced toxicity of Deepwater Horizon slick oil to blue crab (Callinectes sapidus) larvae.

    PubMed

    Alloy, Matthew M; Boube, Idrissa; Griffitt, Robert J; Oris, James T; Roberts, Aaron P

    2015-09-01

    The 2010 Deepwater Horizon oil spill resulted in the accidental release of approximately 700 million L of crude oil into the Gulf of Mexico. Photo-induced toxicity after co-exposure to ultraviolet (UV) radiation is 1 mechanism by which polycyclic aromatic hydrocarbons (PAHs) from oil spills may exert toxicity. Blue crab are an important commercial and ecological resource in the Gulf of Mexico, and their largely transparent larvae may make them sensitive to PAH photo-induced toxicity. The goal of the present study was to examine the sensitivity of early lifestage blue crab (Callinectes sapidus) zoea to slick oil collected during the Deepwater Horizon spill. Blue crab zoea were exposed to 1 of several dilutions of water accommodated fractions from 1 of 2 sources of oil and gradations of natural sunlight in a factorial design. Two 7-h solar exposures were carried out with a recovery period (dark) in between. Survival was found to be UV- and PAH-dependent. Toxicity was observed within the range of surface PAH concentrations reported in the Gulf of Mexico during the Deepwater Horizon spill. These findings indicate that early lifestage blue crab are sensitive to photo-induced toxicity from Deepwater Horizon slick oil.

  17. Supramolecular photomagnetic materials: photoinduced dimerization of ferrocene-based polychlorotriphenylmethyl radicals.

    PubMed

    Ratera, Imma; Ruiz-Molina, Daniel; Vidal-Gancedo, José; Novoa, Juan J; Wurst, Klaus; Letard, Jean-François; Rovira, Concepció; Veciana, Jaume

    2004-02-06

    New ferrocenyl Schiff-base polychlorotriphenylmethyl radicals have been synthesized and characterized. The imino group of one such radical undergoes an irreversible trans to cis structural isomerization induced by light. Such photoinduced isomerization has been monitored by UV/Vis and ESR spectroscopy and also monitored by HPLC. ESR frozen solution experiments at low temperature revealed that the cis isomer dimerizes, showing a strong antiferromagnetic interaction. Although numerous photochromic supramolecular systems have been described, such a photoinduced self-assembly process represents the first example of a one-way photoswitchable magnetic system in which a conversion between a doublet and a singlet ground state species is promoted by a photoinduced dimerization process driven by the formation of hydrogen bonds. DFT calculations on the minimized structure and on the rotational barriers have been performed to establish the origin of such behavior. The effect of the substituents and the media polarity on the photoisomerization of this imine chromophore have also been studied. It has been observed that the efficiency of the process is markedly dependent on the presence and characteristics of electron-donor and electron-acceptor substituents of the ferrocenyl Schiff-base polychlorotriphenylmethyl radicals as well as on the polarity of the solvent.

  18. Deep cytoplasmic rearrangements in axis-respecified Xenopus embryos

    NASA Technical Reports Server (NTRS)

    Denegre, J. M.; Danilchik, M. V.

    1993-01-01

    In fertilized eggs of the frog Xenopus, the vegetal yolk mass rotates away from the future dorsal side (J. P. Vincent and J. Gerhart, 1987, Dev. Biol. 123, 526-539), and a major rearrangement of the deep animal hemisphere cytoplasm produces a characteristic swirl in the prospective dorsal side (M. V. Danilchik and J. M. Denegre, 1991, Development 111, 845-856). The relationship between this swirl and determination of the dorsal-ventral axis was further investigated by attempting to experimentally separate the positions of the swirl and the dorsal-ventral axis. Eggs were obliquely oriented in the gravity field to respecify the direction of yolk mass rotation and the position of the dorsal-ventral axis. When yolk mass rotation occurred in the absence of a sperm, as in activated eggs, a swirl pattern formed on the side away from which the yolk mass had rotated. In fertilized eggs tipped with the sperm entry point (SEP) down or to the side, swirl patterns were always found to form on the side away from which the yolk mass was displaced. However, in eggs tipped SEP up, in which the yolk mass was forced to rotate away from the SEP, more complicated rearrangements were observed in addition to the rotation-oriented swirl. Because the direction of yolk mass rotation was found to be influenced by both gravity and the actual position of the SEP in obliquely oriented eggs (SEP to the side), such complicated rearrangement patterns may result from opposing forces generated by both yolk mass rotation and the expanding sperm aster. Thus, except in cases in which the influences of SEP position and unit gravity opposed each other, it was not possible to experimentally separate the position of the deep cytoplasmic swirl from the direction of yolk mass rotation, and therefore the position of the prospective dorsal side.

  19. Precise detection of rearrangement breakpoints in mammalian chromosomes

    PubMed Central

    Lemaitre, Claire; Tannier, Eric; Gautier, Christian; Sagot, Marie-France

    2008-01-01

    Background Genomes undergo large structural changes that alter their organisation. The chromosomal regions affected by these rearrangements are called breakpoints, while those which have not been rearranged are called synteny blocks. We developed a method to precisely delimit rearrangement breakpoints on a genome by comparison with the genome of a related species. Contrary to current methods which search for synteny blocks and simply return what remains in the genome as breakpoints, we propose to go further and to investigate the breakpoints themselves in order to refine them. Results Given some reliable and non overlapping synteny blocks, the core of the method consists in refining the regions that are not contained in them. By aligning each breakpoint sequence against its specific orthologous sequences in the other species, we can look for weak similarities inside the breakpoint, thus extending the synteny blocks and narrowing the breakpoints. The identification of the narrowed breakpoints relies on a segmentation algorithm and is statistically assessed. Since this method requires as input synteny blocks with some properties which, though they appear natural, are not verified by current methods for detecting such blocks, we further give a formal definition and provide an algorithm to compute them. The whole method is applied to delimit breakpoints on the human genome when compared to the mouse and dog genomes. Among the 355 human-mouse and 240 human-dog breakpoints, 168 and 146 respectively span less than 50 Kb. We compared the resulting breakpoints with some publicly available ones and show that we achieve a better resolution. Furthermore, we suggest that breakpoints are rarely reduced to a point, and instead consist in often large regions that can be distinguished from the sequences around in terms of segmental duplications, similarity with related species, and transposable elements. Conclusion Our method leads to smaller breakpoints than already published ones

  20. Chromosomal rearrangements detected by FISH and G-banding.

    PubMed

    Hou, J W; Wang, T R

    1996-09-01

    Fluorescence in situ hybridization (FISH) using chromosome-specific DNA libraries as painting probes, locus-specific unique sequence (cosmid) probes, and Y-specific repetitive sequences was applied in the analysis of eighteen cases of chromosomal rearrangements of undetermined nature. FISH clarified the origin of the extra or translocated chromosome segments in seventeen patients, one with 2q+, two with 4q+, one each with 6p+, 7p+, 9q+, 10p+, 11q+ and 12p+, two with 13q+, and one each with 15q+, 17p+, 18p+, 20p+, 21p+ and Yq+, as well as the nature of a de novo supernumerary chromosome marker in a previously reported case. By G-banding and molecular cytogenetic studies of the family members, six cases were determined to have unbalanced translocations inherited from the carrier parent. The extra translocated genetic material may cause specific trisomic syndromes, including partial 6p21.3-p23, 9q32-q34.3, 13q32-q34, 15q24-q26, and 17p11.2-p13 trisomies in those patients. A translocated 21q segment on 12p was shown by a painting probe in a patient with Down features. A patient with cat cry syndrome resulting from a loss of the terminal segment of the short arm of chromosome 5 was confirmed by a cosmid probe showing de novo reciprocal translocation between chromosomes 5 and 18:t(5;18) (p13.3;p11.31). With FISH, the extra material on the rearranged chromosome could also be identified as duplicated or translocated. The FISH technique thus provides a method for the analysis of extra structurally abnormal chromosomes (especially in de novo cases), recognizable syndromes (contiguous gene syndromes) caused by translocated deletion from parental balanced chromosome rearrangements, and supernumerary marker chromosomes. FISH subsequent to G-banding is also of great help in the confirmation of preliminary abnormal G-banded karyotypes after a modified destaining procedure. In conclusion, the combination of G-banding and FISH is very useful in the accurate diagnosis of chromosomal

  1. [Clonality lymphoid study through rearrangement analysis of antigen receptor].

    PubMed

    Villamizar-Rivera, Nicolás; Olaya, Natalia

    2015-01-01

    As a rule, malignant lymphoid proliferations are clonal. While most of the time the biological potential can be established through routine pathologic examination and auxiliary techniques, some cases are difficult to classify. Moreover, there are situations in which there are dominant clones whose analysis are important, such as occur in autoimmune diseases and immunodeficiency. This paper presents in an understandable way the main techniques for the study of clonality in lymphoid lesions, i.e. the analysis of rearrangements of antigen receptor genes by multiplex polymerase chain reaction (PCR) based tests.

  2. Controlled order rearrangement encryption for quantum key distribution

    SciTech Connect

    Deng Fuguo; Long, G.L.

    2003-10-01

    A technique is devised to perform orthogonal state quantum key distribution. In this scheme, entangled parts of a quantum information carrier are sent from Alice to Bob through two quantum channels. However, before the transmission, the order of the quantum information carrier in one channel is reordered so that Eve cannot steal useful information. At the receiver's end, the order of the quantum information carrier is restored. The order rearrangement operation in both parties is controlled by a prior shared control key which is used repeatedly in a quantum key distribution session.

  3. Somatic engineering of oncogenic chromosomal rearrangements: a perspective

    PubMed Central

    Maddalo, Danilo; Ventura, Andrea

    2016-01-01

    The ability to engineer specific mutations in mice has proven essential to advancing our understanding of the molecular basis of cancer. Chromosomal rearrangements, a common and clinically relevant class of cancer-causing mutations, have however remained difficult to faithfully recapitulate in vivo. The development of genetic tools for in vivo somatic genome editing has recently overcome this limitation and led to the generation of more sophisticated and accurate preclinical models of human cancers. Here we review the potential applications of these new technologies to the study of tumor biology and discuss their advantages over more conventional strategies, their limitations, and the remaining challenges. PMID:27520450

  4. Investigation of a stereoselective co-mediated rearrangement reaction.

    PubMed

    Carbery, David R; Reignier, Serge; Miller, Neil D; Adams, Harry; Harrity, Joseph P A

    2003-05-30

    A stereocontrolled approach to alpha-alkyl beta-alkynyl cyclohexanones is reported through a Lewis acid mediated rearrangement reaction of enol ethers bearing an Co-alkyne moiety. The reaction proceeds with high levels of stereoselectivity in the presence of Ti- and B-Lewis acids to provide a range of alpha,beta-disubstituted cyclohexanones in high yield although the products are prone to epimerization at the alpha-position in the presence of the B-promoter system. The potential for an enantioselective variant of this process is outlined, and a rationale for the observed stereochemical trends and detailed structural analyses of the ketone products are described.

  5. Thermal rearrangement of novolak resins used in microlithography

    NASA Astrophysics Data System (ADS)

    Hardy, Ricky; Zampini, Anthony; Monaghan, Michael J.; O'Leary, Michael J.; Cardin, William J.; Eugster, Timothy J.

    1995-06-01

    Changes in phenolic-formaldehyde resin properties are described in terms of thermal exposure. At high temperature, resin molecular weight, dissolution properties and chemical composition change depending on the presence or absence of monomers. Without monomer in the resin melt at 220 degree(s)C, resin molecular weight increases with a corresponding decrease in dissolution rate. In the presence of monomer, molecular weight generally decreases. Dissolution rate may fluctuate depending on the monomer mixture. Three,five- Xylenol and 2,3,5-trimethylphenol co-monomers induced the most extreme changes in resin properties with thermal treatment. Resin degradation-recombination processes suggest a classical Friedel-Craft rearrangement mechanism.

  6. Synthesis of Neoglycoconjugates by the Desulfurative Rearrangement of Allylic Disulfides

    PubMed Central

    Crich, David; Yang, Fan

    2009-01-01

    Two series of neoglucosyl donors are prepared based on connection of the allylic disulfide motif to the anomeric center via either a simple O-glycosyl linkage or N-glycosyl amide unit. Conjugation of both sets of donors to cysteine in peptides is demonstrated through classical disulfide exchange followed by the phosphine-mediated desulfurative allylic rearrangement resulting in neoglycopeptides characterized by a simple thioether spacer. The conjugation reaction functions in the absence of protecting groups on both the neoglycosyl donor and peptide in aqueous media at room temperature. PMID:18729514

  7. Developmental arrest at early stages of Chinese hamster embryos homozygous for chromosomal rearrangements

    SciTech Connect

    Sonta, S.; Yamada, M.; Iida, T.; Ohashi, H. )

    1991-03-01

    Forty-three Chinese hamster stocks with autosomal rearrangements produced by X-irradiation were used. These rearrangements, 38 reciprocal translocations and 5 inversions, were chromosomally balanced. Heterozygotes for these rearrangements were all fertile and morphologically normal in both sexes except for one line with growth retardation. By crossing male and female heterozygotes for the same rearrangements, homozygotes were obtained in 37 lines. In the remaining 6 lines (5 with reciprocal translocations and 1 with an inversion), no homozygotes were viable. These 6 lines revealed arrested development of homozygous embryos at the two-cell stage, around the eight-cell stage, and after implantation, respectively. The bands of the breakpoints of rearrangements associated with lethality of homozygous embryos were different for each rearrangement. These results suggest that abnormal expression including embryonic lethality in homozygotes may be due to an influence of genes at the breakpoints.

  8. FOXL2 mutations and genomic rearrangements in BPES.

    PubMed

    Beysen, Diane; De Paepe, Anne; De Baere, Elfride

    2009-02-01

    The FOXL2 gene is one of 10 forkhead genes, the mutations of which lead to human developmental disorders, often with ocular manifestations. Mutations in FOXL2 are known to cause blepharophimosis syndrome (BPES), an autosomal dominant eyelid malformation associated (type I) or not (type II) with ovarian dysfunction, leading to premature ovarian failure (POF). In addition, a few mutations have been described in patients with isolated POF. Here, we review all currently described FOXL2 sequence variations and genomic rearrangements in BPES and POF. Using a combined mutation detection approach, it is possible to identify the underlying genetic defect in a major proportion (88%) of typical BPES patients. Of all genetic defects found in our BPES cohort, intragenic mutations represent 81%. They include missense changes, frameshift and nonsense mutations, in-frame deletions, and duplications, that are distributed along the single-exon gene. Genomic rearrangements comprising both deletions encompassing FOXL2 and deletions located outside its transcription unit, represent 12% and 5% of all genetic defects in our BPES cohort, respectively. One of the challenges of genetic testing in BPES is the establishment of genotype-phenotype correlations, mainly with respect to the ovarian phenotype. Genetic testing should be performed in the context of genetic counseling, however, and should be systematically complemented by a multidisciplinary clinical follow-up. Another challenge for health care professionals involved in BPES is the treatment of the eyelid phenotype and the prevention or treatment of POF.

  9. Compositions and methods for detecting gene rearrangements and translocations

    DOEpatents

    Rowley, Janet D.; Diaz, Manuel O.

    2000-01-01

    Disclosed is a series of nucleic acid probes for use in diagnosing and monitoring certain types of leukemia using, e.g., Southern and Northern blot analyses and fluorescence in situ hybridization (FISH). These probes detect rearrangements, such as translocations involving chromosome band 11q23 with other chromosomes bands, including 4q21, 6q27, 9p22, 19p13.3, in both dividing leukemic cells and interphase nuclei. The breakpoints in all such translocations are clustered within an 8.3 kb BamHI genomic region of the MLL gene. A novel 0.7 kb BamH1 cDNA fragment derived from this gene detects rearrangements on Southern blot analysis with a single BamHI restriction digest in all patients with the common 11q23 translocations and in patients with other 11q23 anomalies. Northern blot analyses are presented demonstrating that the MLL gene has multiple transcripts and that transcript size differentiates leukemic cells from normal cells. Also disclosed are MLL fusion proteins, MLL protein domains and anti-MLL antibodies.

  10. Exploring the Conformational States and Rearrangements of Yarrowia lipolytica Lipase

    PubMed Central

    Bordes, Florence; Barbe, Sophie; Escalier, Pierre; Mourey, Lionel; André, Isabelle; Marty, Alain; Tranier, Samuel

    2010-01-01

    We report the 1.7 Å resolution crystal structure of the Lip2 lipase from Yarrowia lipolytica in its closed conformation. The Lip2 structure is highly homologous to known structures of the fungal lipase family (Thermomyces lanuginosa, Rhizopus niveus, and Rhizomucor miehei lipases). However, it also presents some unique features that are described and discussed here in detail. Structural differences, in particular in the conformation adopted by the so-called lid subdomain, suggest that the opening mechanism of Lip2 may differ from that of other fungal lipases. Because the catalytic activity of lipases is strongly dependent on structural rearrangement of this mobile subdomain, we focused on elucidating the molecular mechanism of lid motion. Using the x-ray structure of Lip2, we carried out extensive molecular-dynamics simulations in explicit solvent environments (water and water/octane interface) to characterize the major structural rearrangements that the lid undergoes under the influence of solvent or upon substrate binding. Overall, our results suggest a two-step opening mechanism that gives rise first to a semi-open conformation upon adsorption of the protein at the water/organic solvent interface, followed by a further opening of the lid upon substrate binding. PMID:20923657

  11. FASEB Summer Research Conference. Genetic Recombination and Chromosome Rearrangements

    SciTech Connect

    Jinks-Robertson, Sue

    2002-02-01

    The 2001 meeting entitled ''Genetic Recombination and Genome Rearrangements'' was held July 21-26 in Snowmass, Colorado. The goal of the meeting was to bring together scientists using diverse approaches to study all aspects of genetic recombination. This goal was achieved by integrating talks covering the genetics, biochemistry and structural biology of homologous recombination, site-specific recombination, and nonhomologous recombination. The format of the meeting consisted of a keynote address on the opening evening, two formal plenary sessions on each of the four full meeting days, a single afternoon workshop consisting of short talks chosen from among submitted abstracts, and afternoon poster sessions on each of the four full meeting days. The eight plenary session were entitled: (1) Recombination Mechanisms, (2) Prokaryotic Recombination, (3) Repair and Recombination, (4) Site-specific Recombination and Transposition, (5) Eukaryotic Recombination I, (6) Genome Rearrangements, (7) Meiosis, and (8) Eukaryotic Recombination II. Each session included a mix of genetic, biochemical and structural talks; talks were limited to 20 minutes, followed by 10 minutes of very lively, general discussion. Much of the data presented in the plenary sessions was unpublished, thus providing attendees with the most up-to-date knowledge of this rapidly-moving field.

  12. Regioselective 1-N-Alkylation and Rearrangement of Adenosine Derivatives.

    PubMed

    Oslovsky, Vladimir E; Drenichev, Mikhail S; Mikhailov, Sergey N

    2015-01-01

    Several methods for the preparation of some N(6)-substituted adenosines based on selective 1-N-alkylation with subsequent Dimroth rearrangement were developed. The proposed methods seem to be effective for the preparation of natural N(6)-isopentenyl- and N(6)-benzyladenosines, which are known to possess pronounced biological activities. Direct 1-N-alkylation of 2',3',5'-tri-O-acetyladenosine and 3',5'-di-O-acetyl-2'-deoxyadenosine with alkyl halides in N,N-dimethylformamide (DMF) in the presence of BaCO3 and KI gave 1-N-substituted derivatives with quantitative yields, whereas 1-N-alkylation of adenosine was accompanied by significant O-alkylation. Moreover, the reaction of trimethylsilyl derivatives of N(6)-acetyl-2',3',5'-tri-O-acetyladenosine and N(6)-acetyl-3',5'-di-O-acetyl-2'-deoxyadenosine with alkyl halides leads to the formation of the stable 1-N-substituted adenosines. Dimroth rearrangement of 1-N-substituted adenosines in aqueous ammonia yields pure N(6)-substituted adenosines.

  13. Results of a comparative study of low energy direct current with radiofrequency ablation in patients with the Wolff-Parkinson-White syndrome.

    PubMed Central

    Lemery, R; Talajic, M; Roy, D; Lavoie, L; Coutu, B; Hii, J T; Radzik, D; Lavallee, E; Cartier, R

    1993-01-01

    OBJECTIVE--To compare two new power sources for catheter ablation in patients with the Wolff-Parkinson-White syndrome. DESIGN--120 consecutive patients with accessory pathways had catheter ablation. Low energy direct current (DC) was used in the first 60 patients and radio-frequency current in the next 60 patients. SETTING--Electrophysiological laboratory of a large heart institute. PATIENTS--72 men and 48 women (mean (SD) age 35 (14) years (range 9-75)). The accessory pathways were in the left free wall in 73 patients. They were posteroseptal in 35 patients, in the right free wall in five, and anteroseptal in seven. There was no significant difference in the clinical or electrophysiological variables between the two ablation groups. RESULTS--Catheter ablation with low energy direct current was successful in 55/60 patients (92%) and radiofrequency energy was successful in 52/60 patients (87%). Low energy direct current was also successful in four of the eight patients in whom radiofrequency ablation had failed. Radiofrequency ablation was successful in two of the five patients in whom low energy direct current ablation had failed. The mean (SD) procedure and fluoroscopy times for successful ablation were 3.2 (1.5) h and 61 (40) min respectively. These times were similar for both power sources. Accessory pathway conduction recurred in 17 patients (28%) who had low energy direct current and four patients (7%) who received radiofrequency energy (p < 0.004). All patients with recurrence of an accessory pathway had successful re-ablation. CONCLUSIONS--Both new power sources successfully ablated accessory pathways, (overall success rate 94% (113/120 patients)). Radiofrequency ablation, however, did not require general anaesthesia and was associated with a significantly lower rate of recurrence of accessory pathway conduction. Therefore radiofrequency should be used initially for ablation. Low energy direct current may be most useful as a back-up in patients in whom

  14. [Wolff-Parkinson-White syndrome. Value of transesophageal atrial stimulation coupled with exercise test for the study of anterograde conduction in the accessory pathway].

    PubMed

    Cebron, J P; Le Marec, H; Victor, J; Chevallier, J C; Borgat, C; Godin, J F

    1989-02-01

    In patients with Wolff-Parkinson-White syndrome the anterograde conduction properties of the accessory pathway determine the ventricular rate in case of atrial fibrillation (AF). Anterograde conduction in the accessory pathway was evaluated in 20 patients (mean age 31 years) by means of transoesophageal atrial pacing with increasing frequency (up to 460 per minute), first at rest, then during exercise on an ergometric bicycle and upon immediate recovery. The exploration was completed by a search for the disappearance of pre-excitation during exercise and after an intravenous injection of ajmaline 1 mg/kg. The shortest cycle (SC) of atrial pacing with 1:1 conduction by the accessory pathway regularly decreased by 80 +/- 26 ms (n = 18), i.e. 27 p. 100 of its value at rest. At immediate recovery SC increased by 40 +/- 53 ms (n = 9). Atrial fibrillation was induced at rest and/or during exercise in 12 patients. The shortest interval (SI) between two pre-excited ventricular complexes was 290 +/- 80 ms (n = 8) at rest and 244 +/- 53 ms (n = 8) during exercise. With a substantial group of values (n = 12) there was good correlation between SC and SI both at rest and during exercise. With a smaller group of values (n = 3) SI was clearly greater than SC, suggesting a concealed conduction in the accessory pathway during atrial fibrillation. Disappearance of pre-excitation during exercise was observed in 4 patients, 3 of whom had a short (less than 250 ms) SC and/or SI.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Prediction, identification, and artificial selection of DNA rearrangements in Rhizobium: toward a natural genomic design.

    PubMed

    Flores, M; Mavingui, P; Perret, X; Broughton, W J; Romero, D; Hernández, G; Dávila, G; Palacios, R

    2000-08-01

    Based on the DNA sequence of the symbiotic plasmid of Rhizobium strain NGR234, we predicted potential rearrangements generated by homologous recombination. All predicted rearrangements were identified experimentally by using a PCR-based methodology. Thus, the predicted and the actual dynamic maps of the replicon coincide. By using an approach that does not involve the introduction of exogenous genetic elements, derivative populations that are pure for specific rearrangements were obtained. We propose that knowledge of the DNA sequence of a genome offers the possibility of designing pathways of sequential rearrangements leading to alternative genomic structures. An experimental strategy to isolate bacterial populations containing the desired structures is discussed.

  16. A New Genomic Evolutionary Model for Rearrangements, Duplications, and Losses That Applies across Eukaryotes and Prokaryotes

    NASA Astrophysics Data System (ADS)

    Lin, Yu; Moret, Bernard M. E.

    Background: Genomic rearrangements have been studied since the beginnings of modern genetics and models for such rearrangements have been the subject of many papers over the last 10 years. However, none of the extant models can predict the evolution of genomic organization into circular unichromosomal genomes (as in most prokaryotes) and linear multichromosomal genomes (as in most eukaryotes). Very few of these models support gene duplications and losses - yet these events may be more common in evolutionary history than rearrangements and themselves cause apparent rearrangements.

  17. Concomitant T-cell receptor alpha and delta gene rearrangements in individual T-cell precursors.

    PubMed Central

    Thompson, S D; Pelkonen, J; Hurwitz, J L

    1990-01-01

    A debate has recently surfaced concerning the degree of precommitment attained by alpha beta and gamma delta T-cell precursors prior to T-cell receptor (TCR) gene rearrangement. It has been suggested that precursors may be precommitted to rearrange either alpha or delta genes, but not both, thus giving rise to alpha beta- and gamma delta-producing T cells, respectively. Alternatively, the precursors may be flexible with regard to potential TCR gene rearrangements. To address this controversy, the gene rearrangements among a group of T-cell hybridomas from fetal, newborn, and early postnatal mouse thymi were examined. Six probes spanning the delta and alpha loci were used in Southern blot analyses to characterize the rearrangements which occurred on homologous chromosomes in each cell. Although homologous chromosomes often rearranged in synchrony within the alpha locus, a number of hybridomas were found which had retained a delta rearrangement on one chromosome and an alpha rearrangement on the second. Results show that a precommitment by T cells to rearrange delta or alpha genes in a mutually exclusive manner is not an absolute feature of mouse thymocyte development. Images PMID:2164690

  18. Molecular screening of pituitary adenomas for gene mutations and rearrangements

    SciTech Connect

    Herman, V.; Drazin, N.Z.; Gonskey, R.; Melmed, S. )

    1993-07-01

    Although pituitary tumors arise as benign monoclonal neoplasms, genetic alterations have not readily been identified in these adenomas. The authors studied restriction fragment abnormalities involving the GH gene locus, and mutations in the p53 and H-, K-, and N-ras genes in 22 human GH cell adenomas. Twenty two nonsecretory adenomas were also examined for p53 and ras gene mutations. Seven prolactinoma DNA samples were tested for deletions in the multiple endocrine neoplasia-1 (MEN-1) locus, as well as for rearrangements in the hst gene, a member of the fibroblast growth factor family. In DNA from GH-cell adenomas, identical GH restriction patterns were detected in both pituitary and lymphocyte DNA in all patients and in one patient with a mixed GH-TSH cell adenoma. Using polymerase chain reaction (PCR)-single stranded conformation polymorphism analysis, no mutations were detected in exons 5, 6, 7 and 8 of the p53 gene in GH cell adenomas nor in 22 nonsecretory adenomas. Codons 12/13 and 61 of H-ras, K-ras, and N-ras genes were also intact on GH cell adenomas and in nonsecretory adenomas. Site-specific probes for chromosome 11q13 including, PYGM, D11S146, and INT2 were used in 7 sporadic PRL-secreting adenomas to detect deletions of the MEN-1 locus on chromosome 11. One patient was identified with a loss of 11p, and the remaining 6 patients did not demonstrate loss of heterozygosity in the pituitary 11q13 locus, compared to lymphocyte DNA. None of these patients demonstrated hst gene rearrangements which also maps to this locus. These results show that p53 and ras gene mutations are not common events in the pathogenesis of acromegaly and nonsecretory tumors. Although hst gene rearrangements and deletions of 11q13 are not associated with sporadic PRl-cell adenoma formation, a single patient was detected with a partial loss of chromosome 11, including the putative MEN-1 site. 31 refs., 5 figs., 2 tabs.

  19. Contribution of canonical nonhomologous end joining to chromosomal rearrangements is enhanced by ATM kinase deficiency.

    PubMed

    Bhargava, Ragini; Carson, Caree R; Lee, Gabriella; Stark, Jeremy M

    2017-01-24

    A likely mechanism of chromosomal rearrangement formation involves joining the ends from two different chromosomal double-strand breaks (DSBs). These events could potentially be mediated by either of two end-joining (EJ) repair pathways [canonical nonhomologous end joining (C-NHEJ) or alternative end joining (ALT-EJ)], which cause distinct rearrangement junction patterns. The relative role of these EJ pathways during rearrangement formation has remained controversial. Along these lines, we have tested whether the DNA damage response mediated by the Ataxia Telangiectasia Mutated (ATM) kinase may affect the relative influence of C-NHEJ vs. ALT-EJ on rearrangement formation. We developed a reporter in mouse cells for a 0.4-Mbp deletion rearrangement that is formed by EJ between two DSBs induced by the Cas9 endonuclease. We found that disruption of the ATM kinase causes an increase in the frequency of the rearrangement as well as a shift toward rearrangement junctions that show hallmarks of C-NHEJ. Furthermore, ATM suppresses rearrangement formation in an experimental condition, in which C-NHEJ is the predominant EJ repair event (i.e., expression of the 3' exonuclease Trex2). Finally, several C-NHEJ factors are required for the increase in rearrangement frequency caused by inhibition of the ATM kinase. We also examined ATM effectors and found that H2AX shows a similar influence as ATM, whereas the influence of ATM on this rearrangement seems independent of 53BP1. We suggest that the contribution of the C-NHEJ pathway to the formation of a 0.4-Mbp deletion rearrangement is enhanced in ATM-deficient cells.

  20. Highly rearranged mitochondrial genome in Nycteria parasites (Haemosporidia) from bats

    PubMed Central

    Karadjian, Gregory; Hassanin, Alexandre; Saintpierre, Benjamin; Gembu Tungaluna, Guy-Crispin; Ariey, Frederic; Ayala, Francisco J.; Landau, Irene; Duval, Linda

    2016-01-01

    Haemosporidia parasites have mostly and abundantly been described using mitochondrial genes, and in particular cytochrome b (cytb). Failure to amplify the mitochondrial cytb gene of Nycteria parasites isolated from Nycteridae bats has been recently reported. Bats are hosts to a diverse and profuse array of Haemosporidia parasites that remain largely unstudied. There is a need to obtain more molecular data from chiropteran parasites. Such data would help to better understand the evolutionary history of Haemosporidia, which notably include the Plasmodium parasites, malaria’s agents. We use next-generation sequencing to obtain the complete mitochondrial genome of Nycteria parasites from African Nycteris grandis (Nycteridae) and Rhinolophus alcyone (Rhinolophidae) and Asian Megaderma spasma (Megadermatidae). We report four complete mitochondrial genomes, including two rearranged mitochondrial genomes within Haemosporidia. Our results open outlooks into potentially undiscovered Haemosporidian diversity. PMID:27528689

  1. Electronic Structure Rearrangements in Hybrid Ribozyme/Protein Catalysis

    NASA Astrophysics Data System (ADS)

    Kang, Jiyoung; Kino, Hiori; Field, Martin J.; Tateno, Masaru

    2017-04-01

    We analyzed the electronic structural changes that occur in the reaction cycle of a biological catalyst composed of RNA and protein, and elucidated the dynamical rearrangements of the electronic structure that was obtained from our previous study in which ab initio quantum mechanics/molecular mechanics molecular dynamics simulations were performed. Notable results that we obtained include the generation of a reactive HOMO that is responsible for bond formation in the initial stages of the reaction, and the appearance of a reactive LUMO that is involved in the bond rupture that leads to products. We denote these changes as dynamical induction of the reactive HOMO (DIRH) and LUMO (DIRL), respectively. Interestingly, we also find that the induction of the reactive HOMO is enhanced by the formation of a low-barrier hydrogen bond (LBHB), which, to the best of our knowledge, represents a novel role for LBHBs in enzymatic systems.

  2. Hydrogen Ion-Molecule Isotopomer Collisions: Charge Transfer and Rearrangement

    NASA Astrophysics Data System (ADS)

    Wang, J. G.; Stancil, P. C.

    A survey of existing data for collisions of isotopes of hydrogen atoms, ions, and molecules is presented. The survey was limited to atom - diatom ionic collisions and to energies generally less than about 10 keV/u. The processes include particle-rearrangement and charge transfer, including both dissociative and non-dissociative channels, with an emphasis on state-to-state (or state-selected) data, where available. Since the last survey (Linder, Janev and Botero 1995), a small number of investigations for deuterium and tritium ion-diatom systems have been performed, with some involving state-resolved data, which include the initial-state-resolved and state-to-state processes. While some progress has been made since the last survey, the database involving hydrogen isotope collisional processes, both total and state- resolved, is far from complete.

  3. Sequential Assembly of Magnetic Prussian Blue Films with Photo-Induced Magnetism

    NASA Astrophysics Data System (ADS)

    Meisel, Mark W.

    2004-11-01

    Despite interest in the area of molecule-based magnets, there are few efforts to investigate magnetism in monolayers, surface layers, and other thin films based on these materials. New synthetic methods developed by our groups now permit deposition of single layer and multilayer thin films of cyanometallate molecule-based magnet systems. These monolayers and surface films are inherently anisotropic, thereby allowing magnetic characterizations that are only possible because of our method of fabrication. Two examples will be presented. The distance dependence of dipolar interactions on magnetic order is illustrated by comparing a monolayer, bilayer, and multilayers of a mixed organic/inorganic Fe^3+/Ni^2+ cyanometallate two-dimensional network. The magnetometry results demonstrate the influence of dipolar interactions at an interlayer separation of greater than 35 ÅSecondly, anisotropic response of the photoinduced magnetism in a thin film of Rb_jCo_k[Fe(CN)_6]l \\cdot nH_2O, which experiences a ferrimagnetic transition near 20 K, has been discovered. The photo-induced magnetism may result in a net increase or decrease of the total magnetization of the sample when the externally applied magnetic field is oriented parallel or perpendicular to the plane of the films. The strength of this anisotropy depends on the thickness of the film and the size of the magnetic domains, and the photo-induced magnetism was effective in magnetic fields up to 27 T while at 4.7 K. This work, co-authored with D. R. Talham, was performed with J.-H. Park, F. Frye, Y.-D. Huh, E. Čižmár, and S. Lane, and was supported, in part, by NSF DMR-0305371.

  4. Rearrangements of highly polymorphic regions near telomeres of Saccharomyces cerevisiae.

    PubMed Central

    Horowitz, H; Thorburn, P; Haber, J E

    1984-01-01

    We have examined the mitotic and meiotic properties of telomeric regions in various laboratory strains of yeast. Using a sequence (Y probe) derived from a cloned yeast telomere (J. Szostak and E. Blackburn, Cell 29:245-255, 1982), we found that various strains of Saccharomyces cerevisiae show extensive polymorphisms of restriction endonuclease fragment length. Some of the variation in the lengths of telomeric fragments appears to be under the control of a small number of genes. When DNA from various strains was digested with endonuclease KpnI, nearly all of the fragments homologous to the Y probe were found to be of different size. The pattern of fragments in different strains was extremely variable, with a greater degree of polymorphism than that observed for fragments containing the mobile TY1 element. Tetrad analysis of haploid meiotic segregants from diploids heterozygous for many different Y-homologous KpnI fragments revealed that most of them exhibited Mendelian (2:0) segregation. However, only a small proportion of these fragments displayed the obligate 2:2 parental segregation expected of simple allelic variants at the same chromosome end. From the segregations of these fragments, we concluded that some yeast telomeres lack a Y-homologous sequence and that the chromosome arms containing a Y-homologous sequence are different among various yeast strains. Regions near yeast telomeres frequently undergo rearrangement. Among eight tetrads from three different diploids, we have found three novel Y-homologous restriction fragments that appear to have arisen during meiosis. In all three cases, the appearance of a new fragment was accompanied by the loss of another band. In one of these cases, the rearrangement leading to a novel fragment arose in an isogenic diploid, in which both homologous chromosomes should have been identical. Among these same tetrads we also found examples of apparent mitotic gene conversions and mitotic recombination involving telemetric

  5. Genome rearrangement affects RNA virus adaptability on prostate cancer cells.

    PubMed

    Pesko, Kendra; Voigt, Emily A; Swick, Adam; Morley, Valerie J; Timm, Collin; Yin, John; Turner, Paul E

    2015-01-01

    Gene order is often highly conserved within taxonomic groups, such that organisms with rearranged genomes tend to be less fit than wild type gene orders, and suggesting natural selection favors genome architectures that maximize fitness. But it is unclear whether rearranged genomes hinder adaptability: capacity to evolutionarily improve in a new environment. Negative-sense non-segmented RNA viruses (order Mononegavirales) have specific genome architecture: 3' UTR - core protein genes - envelope protein genes - RNA-dependent RNA-polymerase gene - 5' UTR. To test how genome architecture affects RNA virus evolution, we examined vesicular stomatitis virus (VSV) variants with the nucleocapsid (N) gene moved sequentially downstream in the genome. Because RNA polymerase stuttering in VSV replication causes greater mRNA production in upstream genes, N gene translocation toward the 5' end leads to stepwise decreases in N transcription, viral replication and progeny production, and also impacts the activation of type 1 interferon mediated antiviral responses. We evolved VSV gene-order variants in two prostate cancer cell lines: LNCap cells deficient in innate immune response to viral infection, and PC-3 cells that mount an IFN stimulated anti-viral response to infection. We observed that gene order affects phenotypic adaptability (reproductive growth; viral suppression of immune function), especially on PC-3 cells that strongly select against virus infection. Overall, populations derived from the least-fit ancestor (most-altered N position architecture) adapted fastest, consistent with theory predicting populations with low initial fitness should improve faster in evolutionary time. Also, we observed correlated responses to selection, where viruses improved across both hosts, rather than suffer fitness trade-offs on unselected hosts. Whole genomics revealed multiple mutations in evolved variants, some of which were conserved across selective environments for a given gene

  6. Synthesis and rearrangements of aminosubstituted ferra- and ruthenatricarbaboranes.

    PubMed

    Holub, Josef; Grüner, Bohumír; Perekalin, Dmitry S; Golovanov, Denis G; Lyssenko, Konstantin A; Petrovskii, Pavel V; Kudinov, Alexander R; Stíbr, Bohumil

    2005-03-21

    A room-temperature reaction between the [7-tBuNH-nido-7,8,9-C3B8H10]- anion (1a) and [Cp*RuCl]4 leads to the ruthenatricarbollide [1-Cp*-12-tBuNH-1,2,4,12-RuC3B8H10] (2) (yield 85%). Analogously, the room-temperature photochemical reaction of 1a with [CpFe(C6H6)]PF6 gives the previously reported iron complex [1-Cp-12-tBuNH-1,2,4,12-FeC3B8H10] (3) (yield 82%). Both reactions are associated with extensive polyhedral rearrangement, which occurs under very mild conditions and brings the carbon atoms to positions of maximum separation within the framework. Compounds 2 and 3 were also surprisingly obtained via complexation of the isomeric [8-tBuNH-nido-7,8,9-C3B8H10]- (1b) anion. Complex 2 rearranges further to [1-Cp*-10-tBuNH-1,2,4,10-RuC3B8H10] (4) upon refluxing in xylene (145 degrees C). Density functional theory calculations at the B3LYP/SDD level were used to estimate relative stabilities of these metallacarborane isomers. Compounds 2 and 4, along with the 11-vertex closo compounds [1-Cp*-1,2,3,10-RuC3B7H10] (5) and [1-Cp*-10-tBuNH-1,2,3,10-RuC3B7H9] (6), were also isolated from the reaction between [Cp*RuCl2]2 and 1a in boiling xylene. The structure of 2 was established by an X-ray diffraction study, and the constitution of all compounds was determined unambiguously by multinuclear NMR spectroscopy, mass spectrometry, and elemental analyses.

  7. Deuterium enrichment by selective photoinduced dissociation of a multihalogenated organic compound

    DOEpatents

    Marling, John B.; Herman, Irving P.

    1981-01-01

    A method for deuterium enrichment by photoinduced dissociation which uses as the deuterium source a multihalogenated organic compound selected from the group consisting of a dihalomethane, a trihalomethane, a 1,2-dihaloethene, a trihaloethene, a tetrahaloethane and a pentahaloethane. The multihalogenated organic compound is subjected to intense infrared radiation at a preselected wavelength to selectively excite and thereby induce dissociation of substantially only those molecules containing deuterium to provide a deuterium enriched dissociation product. The deuterium enriched product may be combusted with oxygen to provide deuterium enriched water. The deuterium depleted undissociated molecules may be redeuterated by treatment with a deuterium source such as water.

  8. Image storage in coumarin-based copolymer thin films by photoinduced dimerization.

    PubMed

    Gindre, Denis; Iliopoulos, Konstantinos; Krupka, Oksana; Champigny, Emilie; Morille, Yohann; Sallé, Marc

    2013-11-15

    We report a technique to encode grayscale digital images in thin films composed of copolymers containing coumarins. A nonlinear microscopy setup was implemented and two nonlinear optical processes were used to store and read information. A third-order process (two-photon absorption) was used to photoinduce a controlled dimer-to-monomer ratio within a defined tiny volume in the material, which corresponds to each recorded bit of data. Moreover, a second-order process (second-harmonic generation) was used to read the stored information, which has been found to be highly dependent upon the monomer-to-dimer ratio.

  9. Tuning of photoinduced energy transfer in a bichromophoric coumarin supermolecule by cation binding

    SciTech Connect

    Valeur, B.; Pouget, J.; Bourson, J.; Kaschke, M.; Ernsting, N.P.

    1992-08-06

    This paper discussed tuning of photoinduced electronic energy transfer in two coumarins linked by a pentakis (ethylene oxide) spacer by Pb{sup 2+} binding in acetonitrile and propylene carbonate. The ligand:metal ratio is observed to be 1:1 in acetonitrile with a significant increase in efficiency and rate of energy transfer as compared to propylene carbonate, which has a ratio of 1:3. This may be due to a different complex structure in the two solvents. 12 refs., 10 figs., 1 tab.

  10. Graphene/CdTe heterostructure solar cell and its enhancement with photo-induced doping

    SciTech Connect

    Lin, Shisheng Chen, Hongsheng; Li, Xiaoqiang; Zhang, Shengjiao; Wang, Peng; Xu, Zhijuan; Zhong, Huikai; Wu, Zhiqian

    2015-11-09

    We report a type of solar cell based on graphene/CdTe Schottky heterostructure, which can be improved by surface engineering as graphene is atomic thin. By coating a layer of ultrathin CdSe quantum dots onto graphene/CdTe heterostructure, the power conversion efficiency is increased from 2.08% to 3.10%. Photo-induced doping is mainly accounted for this enhancement, as evidenced by field effect transport, Raman, photoluminescence, and quantum efficiency measurements. This work demonstrates a feasible way of improving the performance of graphene/semiconductor heterostructure solar cells by combining one dimensional with two dimensional materials.

  11. Photoinduced charge transfer involving a MoMo quadruply bonded complex to a perylene diimide.

    PubMed

    Alberding, Brian G; Brown-Xu, Samantha E; Chisholm, Malcolm H; Epstein, Arthur J; Gustafson, Terry L; Lewis, Sharlene A; Min, Yong

    2013-04-21

    Evidence, based on femtosecond transient absorption and time resolved infrared spectroscopy, is presented for photoinduced charge transfer from the Mo2δ orbital of the quadruply bonded molecule trans-Mo2(T(i)PB)2(BTh)2, where T(i)PB = 2,4,6-triisopropyl benzoate and BTh = 2,2'-bithienylcarboxylate, to di-n-octyl perylene diimide and di-n-hexylheptyl perylene diimide in thin films and solutions of the mixtures. The films show a long-lived charge separated state while slow back electron transfer, τBET ~ 500 ps, occurs in solution.

  12. Photoinduced Electron Transfer in Ordered Macromolecular Assemblies. Final report for May 1, 1988 - June 30, 2002

    SciTech Connect

    Jones, G.

    2005-02-11

    The final report describes studies over a 13 year period having to do with photoinduced electron transfer for active chromophores and redox agents, including assembly of the components in water soluble polymers or polypeptides. The findings include observation of long range charge separation and electron transport using laser phototransient spectroscopy. The systems targeted in these studies include peptide assemblies for which helical conformations and aggregation are documented. Oligomeric peptides modified with non-native redox active groups were also selected for investigation. Highly charged polymers or peptides were investigated as host agents that resemble proteins. The overall goal of these investigations focused on the design and characterization of systems capable of artificial photosynthesis.

  13. Molecular orbital assistance in the design of intramolecular and photoinduced electron transfer systems

    NASA Astrophysics Data System (ADS)

    Petsalakis, Ioannis D.; Theodorakopoulos, Giannoula

    2012-02-01

    A theoretical approach is described for the design of donor-acceptor intramolecular charge transfer (ICT) systems and for photoinduced electron transfer (PET) hybrids of fullerene, based on orbital level diagrams of the separate donor and acceptor moieties. Minimization of the HOMO-LUMO (highest occupied-lowest unoccupied orbital) gap in ICT systems, translates to a requirement for near degeneracy of the HOMO of the donor and LUMO of the acceptor, determined separately for the two moieties by density functional theory calculations. Similarly, near degeneracy of the LUMO of the donor and LUMO of the acceptor moieties would indicate the possibility of PET in the combined hybrid.

  14. Photoinduced Barkhausen effect in the ferromagnetic semiconductor (Ga,Mn)As.

    PubMed

    Astakhov, G V; Schwittek, J; Schott, G M; Gould, C; Ossau, W; Brunner, K; Molenkamp, L W

    2011-01-21

    Magnetization of ferromagnetic materials commonly occurs via random jumps of domain walls between pinning sites, a phenomenon known as the Barkhausen effect. Using strongly focused light pulses of appropriate power and duration we demonstrate the ability to selectively activate single jumps in the domain wall propagation in (Ga,Mn)As, manifesting itself as a discrete photoinduced domain wall creep as a function of illumination time. The propagation velocity can be increased over 7 orders of magnitude varying the illumination power density and the magnetic field.

  15. Primary ultrafast events preceding the photoinduced proton transfer from pyranine to water

    NASA Astrophysics Data System (ADS)

    Tran-Thi, T.-H.; Gustavsson, T.; Prayer, C.; Pommeret, S.; Hynes, James T.

    2000-10-01

    Femtosecond fluorescence and absorption spectroscopies are used to probe the early events of the photoinduced proton transfer (PT) from pyranine to water. The process is found to involve two ultrafast steps (300 fs and 2.5 ps) which precede the relatively slow (87 ps) PT step. From the comparative study of the properties of the excited acid and its conjugate anion in various aqueous and alcoholic media, these ultrafast steps are identified as the solvation dynamics of the locally excited (LE) state of the acid and its subsequent relaxation to an intermediate electronic state, whose nature is discussed.

  16. Photoinduced Reconfiguration Cycle in a Molecular Adsorbate Layer Studied by Femtosecond Inner-Shell Photoelectron Spectroscopy

    SciTech Connect

    Dachraoui, H.; Michelswirth, M.; Bartz, P.; Pfeiffer, W.; Heinzmann, U.; Siffalovic, P.; Schaefer, C.; Schnatwinkel, B.; Mattay, J.; Drescher, M.

    2011-03-11

    A time-resolved study of core-level chemical shifts in a monolayer of aromatic molecules reveals complex photoinduced reaction dynamics. The combination of electron spectroscopy for chemical analysis and ultrashort pulse excitation in the extreme ultraviolet allows performing time-correlated 4d-core-level spectroscopy of iodine atoms that probe the local chemical environment in the adsorbate molecule. The selectivity of the method unveils metastable molecular configurations that appear about 50 ps after the excitation and are efficiently quenched back to the ground state.

  17. Decay of photoinduced oscillations of the optical reflection coefficient of bismuth

    SciTech Connect

    Semenov, A. L.

    2013-07-15

    A model describing the decay of photoinduced oscillations of the optical reflection coefficient R of bismuth is constructed, taking the crystal lattice anharmonicity into account. The decay time of oscillations of R is calculated as a function of the energy density of a laser pulse. The results of calculations explain the experimental data on the anomalously strong decay of oscillations of the optical reflection coefficient of bismuth (the decay time decreases by more than an order of magnitude with an increase in the laser pulse energy density from 0 to 4 mJ/cm{sup 2})

  18. Fourier transform infrared spectrum of the radical cation of beta-carotene photoinduced in photosystem II.

    PubMed

    Noguchi, T; Mitsuka, T; Inoue, Y

    1994-12-19

    A Fourier-transform infrared (FTIR) spectrum of the radical cation of beta-carotene photoinduced in photosystem II (PSII) membranes was obtained at 80K under oxidizing conditions, by utilizing the light-induced FTIR difference technique. Formation of the beta-carotene cation was monitored with the electronic absorption band at 993 nm. An FTIR spectrum of a chemically-generated beta-carotene cation in chloroform was also measured and compared with the spectrum of PSII. Since the FTIR bands of carotenoid cation have characteristic features with strong intensities, they can be useful markers in studying the reaction of carotenoid in PSII.

  19. Photoinduced electron transfer in rigidly linked dimethoxynapthalene-N-methylpyridinium donor-acceptor molecules

    NASA Astrophysics Data System (ADS)

    Clayton, Andrew H. A.; Ghiggino, Kenneth P.; Wilson, Gerard J.; Keyte, Peter J.; Paddon-Row, Michael N.

    1992-07-01

    Photoinduced electron transfer (ET) is studied in a series of novel molecules containing a dimethoxynaphthalene (DMN) donor and either a pyridine (P) or N-methylpyridinium (P-Me +) acceptor covalently linked via a rigid nonbornalogous bridge ( n sigma bonds in length). ET rates of the order of 10 10 s -1 were measured for the DMN- n-P-Me + series ( n = 4, 6), while no appreciable ET was observed for the DMN- n-P compounds. Electronic and nuclear factors are discussed and the results rationalized in terms of Marcus—Hush and non-adiabatic ET theories.

  20. Linear and Nonlinear Optical Spectroscopy at the Nanoscale with Photoinduced Force Microscopy.

    PubMed

    Jahng, Junghoon; Fishman, Dmitry A; Park, Sung; Nowak, Derek B; Morrison, Will A; Wickramasinghe, H Kumar; Potma, Eric O

    2015-10-20

    The enormous advances made in nanotechnology have also intensified the need for tools that can characterize newly synthesized nanoaterials with high sensitivity and with high spatial resolution. Many existing tools with nanoscopic resolution or better, including scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning tunneling microscopy (STM) methods, can generate highly detailed maps of nanoscopic structures. However, while these approaches provide great views of the morphological properties of nanomaterials, it has proven more challenging to derive chemical information from the corresponding images. To address this issue, attempts have been made to dress existing nanoscopy methods with spectroscopic sensitivity. A powerful approach in this direction is the combination of scan probe techniques with optical illumination, which aims to marry the nanoscopic resolution provided by a sharp tip with the chemical selectivity provided by optical spectroscopy. Examples of this approach include existing techniques such as scattering-type scanning near-field optical microscopy and tip-enhanced Raman spectroscopy. A new and emerging technique in this direction is photoinduced force microscopy (PiFM), which enables spectroscopic probing of materials with a spatial resolution well under 10 nm. In PiFM, the sample is optically excited and the response of the material is probed directly in the near-field by reading out the time-integrated force between the tip and the sample. Because the magnitude of the force is dependent on the photoinduced polarization in the sample, PiFM exhibits spectroscopic sensitivity. The photoinduced forces measured in PiFM are spatially confined on the nanometer scale, which translates into a very high spatial resolution even under ambient conditions. The PiFM approach is compatible with a wide range optical excitation frequencies, from the visible to the mid-infrared, enabling nanoscale imaging contrast based on either

  1. Time-Resolved Studies of Photoinduced Birefringence in Azobenzene Dye-Doped Polymer Films

    DTIC Science & Technology

    2008-10-01

    state, where the fairly limited work has been done [8,9]. Here we report on transient photoinduced birefrin- gence ( PIB ) measurements on several azo...response time ranges from within 20ns to more than 200 μs. Our results show the response time of PIB to be sys- tematically related to the size of the...lowest optical transition energy. Furthermore, our results suggest that PIB effects can be used to discriminate between0003-6935/08/285074-04$15.00/0

  2. Model of photo-induced neutral-ionic phase transition in organic charge-transfer salts

    NASA Astrophysics Data System (ADS)

    Yartsev, V. M.

    1998-01-01

    One-dimensional donor-acceptor mixed chains are modeled by a periodic DADA tetramer. Electron coupling to intramolecular vibrations are taken into account explicitly. Generalized adiabatic potentials are calculated for the cases of regular and dimerized stacks which are characteristic, respectively, of quasi-neutral (N) and quasi-ionic (I) phases of a tetrathiafulvalene-chloranil compound. A sharp difference in life-times of photo-induced I-states in the N-phase and N-states in the I-phase is discussed within the periodic DADA tetramer model.

  3. Photoinduced cytotoxicity by a platinum diimine complex employing magnetite-silica nanocomposites as delivery vehicles.

    PubMed

    Zhang, Zhigang; Li, Haisha; Dai, Ruihui; Chai, Aiyun

    2015-10-01

    Tartaric acid-modified core-shell magnetite-silica nanocomposites were prepared by a sol-gel method, and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and dynamic light scattering. Then the nanocomposites were employed as carriers of a photoactive platinum diimine complex. Photoinduced cytotoxicity by the photosensitizer-loaded nanocomposites in different human carcinoma cells has been studied by cell viability assay. The results suggest that the as-synthesized nanocomposites have good stability in water, and the cytotoxicity induced by the platinum diimine complex in red light can be significantly enhanced when the photosensitizer is loaded with the magnetic nanocomposites.

  4. Spontaneous photoinduced patterning of azo-dye polymer films: the facts

    SciTech Connect

    Hubert, Christophe

    2007-08-15

    We describe the spontaneous photoinduced patterning of azo-dye polymer films. We have observed that the illumination of an azo-dye polymer film by a uniform single laser beam with normal incidence leads to a self-structurization process that results in the formation of well-ordered submicrometer-sized structures whose organization depends on the light polarization direction. A modulation depth as high as 100 nm can be achieved. The influence of several experimental parameters on the structure formation is studied. Results are discussed and confronted to different models and phenomena already investigated in the literature. A physical origin to this peculiar photopatterning process is proposed.

  5. Deuterium enrichment by selective photo-induced dissociation of an organic carbonyl compound

    DOEpatents

    Marling, John B.

    1981-01-01

    A method for producing a deuterium enriched material by photoinduced dissociation which uses as the working material a gas phase photolytically dissociable organic carbonyl compound containing at least one hydrogen atom bonded to an atom which is adjacent to a carbonyl group and consisting of molecules wherein said hydrogen atom is present as deuterium and molecules wherein said hydrogen atom is present as another isotope of hydrogen. The organic carbonyl compound is subjected to intense infrared radiation at a preselected wavelength to selectively excite and thereby induce dissociation of the deuterium containing species to yield a deuterium enriched stable molecular product. Undissociated carbonyl compound, depleted in deuterium, is preferably redeuterated for reuse.

  6. Photoinduced holographic surface relief gratings in thin self-developing dichromated polymer films: parametric study

    NASA Astrophysics Data System (ADS)

    Beaulieu, Rene M.; Lessard, Roger A.; Bolte, Michel

    1998-09-01

    Photoinduced holographic surface relief gratings have been fabricate din dichromated poly(acrylic acid) films. These gratings are formed in darkness subsequent to the illumination at 442 nm and they are obtained without any chemical treatment or wet processing. The influence of chemical parameters, such as ammonium dichromate and dimethylformamide concentrations, on the holographic characteristics of these gratings have been investigated. Holographic characteristics of the recording medium such as diffraction efficiency as a function of exposure, ammonium dichromate and dimethylformamide concentrations, and spatial frequency are presented in this paper.

  7. POLARON DYNAMICS. Long-lived photoinduced polaron formation in conjugated polyelectrolyte-fullerene assemblies.

    PubMed

    Huber, Rachel C; Ferreira, Amy S; Thompson, Robert; Kilbride, Daniel; Knutson, Nicholas S; Devi, Lekshmi Sudha; Toso, Daniel B; Challa, J Reddy; Zhou, Z Hong; Rubin, Yves; Schwartz, Benjamin J; Tolbert, Sarah H

    2015-06-19

    The efficiency of biological photosynthesis results from the exquisite organization of photoactive elements that promote rapid movement of charge carriers out of a critical recombination range. If synthetic organic photovoltaic materials could mimic this assembly, charge separation and collection could be markedly enhanced. We show that micelle-forming cationic semiconducting polymers can coassemble in water with cationic fullerene derivatives to create photoinduced electron-transfer cascades that lead to exceptionally long-lived polarons. The stability of the polarons depends on the organization of the polymer-fullerene assembly. Properly designed assemblies can produce separated polaronic charges that are stable for days or weeks in aqueous solution.

  8. Perovskites for Photovoltaics in the Spotlight: Photoinduced Physical Changes and Their Implications.

    PubMed

    Gottesman, Ronen; Zaban, Arie

    2016-02-16

    Organic-inorganic halide perovskites are in consensus to revolutionize the field of photovoltaics and optoelectronic devices due to their superior optical and electronic properties which are unprecedented in comparison to those of other solution processed semiconductors. These hybrid materials are used as light absorbers and also as charge carriers which makes them very versatile to be implemented and studied in a multitude of fields. Traditionally, the working paradigm in solar cells and optoelectronic devices' characterization has been that the properties of photovoltaic materials remain stable following illumination of varying times and intensities. However, recently there has been a growing number of reports on prolonged illumination-dependent physical changes in perovskite films and perovskite based devices. The changes are reversible and range from structural transformations and differences in optical characteristics, to an increase in optoelectronic properties and physical parameters. In this Account, we review the physical changes in three reported model systems which display changes under prolonged illumination of light intensities of ∼0.01-1 sun. The three systems are (i) a free-standing perovskite film on a glass substrate, (ii) a symmetrical system with nonselective electrical contacts, and (iii) a working perovskite solar cell (either a planar or a porous structure). We examine each model system and discuss its photoinduced physical changes and conclude with the implications on future experimentation design, data analysis, and characterization that involve organic-inorganic halide perovskites illumination. Since hybrid perovskites are considered to be mixed ionic-electronic conductors in nature, ions that migrate in the perovskite under electrical fields can influence its properties. Therefore, an important distinction is made between photoinduced effects and photo and electric field induced effects. Thus, photoinduced effects are designated as

  9. Photoinduced intramolecular charge transfer process of betaine pyridinium: A theoretical spectroscopic study

    NASA Astrophysics Data System (ADS)

    Perrier, Aurélie; Aloïse, Stéphane; Pawlowska, Zuzanna; Sliwa, Michel; Maurel, François; Abe, Jiro

    2011-10-01

    Using Time-Dependent Density Functional Theory and taking into account bulk solvent effects, we investigate the absorption and emission spectra of a betaine pyridinium molecule, the 2-(1-pyridinio) benzimidazolate (SBPa). This molecule exhibits strong photoinduced intramolecular charge transfer (ICT). We have identified two different electronic states involved, respectively, in the strong bathochromic ICT absorption band (S 2) and in the moderate emission band (S 1). The ICT process is analyzed in terms of charge distribution and dipole moment evolutions upon photoexcitation. These results are compared with steady-state spectroscopic measurements.

  10. Photo-induced conductance fluctuations in mesoscopic Ge/Si systems with quantum dots

    SciTech Connect

    Stepina, N. P.; Dvurechenskii, A. V.; Nikiforov, A. I.; Moers, J.; Gruetzmacher, D.

    2014-08-20

    We study the evolution of electron transport in strongly localized mesoscopic system with quantum dots under small photon flux. Exploring devices with narrow transport channels lead to the observation of giant fluctuations of the photoconductance, which is attributed to the strong dependence of hopping current on the filling of dots by holes. In our experiments, single-photon mode operation is indicated by the linear dependence of the frequency of photo-induced fluctuations on the light intensity and the step-like response of conductance on the pulse excitation. The effect of the light wavelength, measurement temperature, size of the conductive channel on the device efficiency are considered.

  11. Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

    PubMed Central

    Krüger, Sebastian

    2014-01-01

    Summary This review summarizes the application of the divinylcyclopropane–cycloheptadiene rearrangement in synthetic organic chemistry. A brief overview of the new mechanistic insights concerning the title reaction is provided as well as a condensed account on the biological relevance of the topic. Heteroatom variants of this rearrangement are covered briefly. PMID:24605138

  12. Stereoselective Synthesis of Quaternary Carbons via the Dianionic Ireland–Claisen Rearrangement

    PubMed Central

    2015-01-01

    A dianionic Ireland–Claisen rearrangement of chiral, nonracemic α-methyl-β-hydroxy allylic esters has been developed that proceeds with high diastereoselectivity and provides products containing three contiguous stereogenic carbons, including a quaternary center. The potential utility of the rearrangement for complex molecule synthesis is also demonstrated. PMID:24735235

  13. Catalytic enantioselective [2,3]-rearrangements of amine N-oxides.

    PubMed

    Bao, Hongli; Qi, Xiangbing; Tambar, Uttam K

    2011-02-09

    The first Pd-catalyzed enantioselective [2,3]-rearrangement of allylic amine N-oxides is described, which formally represents an asymmetric Meisenheimer rearrangement. The mild reaction conditions enable the synthesis of chiral nonracemic aliphatic allylic alcohol derivatives with reactive functional groups. On the basis of preliminary studies, a cyclization-mediated mechanism is proposed.

  14. On the association between chromosomal rearrangements and genic evolution in humans and chimpanzees

    PubMed Central

    Marques-Bonet, Tomàs; Sànchez-Ruiz, Jesús; Armengol, Lluís; Khaja, Razi; Bertranpetit, Jaume; Lopez-Bigas, Núria; Rocchi, Mariano; Gazave, Elodie; Navarro, Arcadi

    2007-01-01

    Background The role that chromosomal rearrangements might have played in the speciation processes that have separated the lineages of humans and chimpanzees has recently come into the spotlight. To date, however, results are contradictory. Here we revisit this issue by making use of the available human and chimpanzee genome sequence to study the relationship between chromosomal rearrangements and rates of DNA sequence evolution. Results Contrary to previous findings for this pair of species, we show that genes located in the rearranged chromosomes that differentiate the genomes of humans and chimpanzees, especially genes within rearrangements themselves, present lower divergence than genes elsewhere in the genome. Still, there are considerable differences between individual chromosomes. Chromosome 4, in particular, presents higher divergence in genes located within its rearrangement. Conclusion A first conclusion of our analysis is that divergence is lower for genes located in rearranged chromosomes than for those in colinear chromosomes. We also report that non-coding regions within rearranged regions tend to have lower divergence than non-coding regions outside them. These results suggest an association between chromosomal rearrangements and lower non-coding divergence that has not been reported before, even if some chromosomes do not follow this trend and could be potentially associated with a speciation episode. In summary, without excluding it, our results suggest that chromosomal speciation has not been common along the human and chimpanzee lineage. PMID:17971225

  15. Inverted genomic segments and complex triplication rearrangements are mediated by inverted repeats in the human genome

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We identified complex genomic rearrangements consisting of intermixed duplications and triplications of genomic segments at the MECP2 and PLP1 loci. These complex rearrangements were characterized by a triplicated segment embedded within a duplication in 11 unrelated subjects. Notably, only two brea...

  16. Lecture Capture with Real-Time Rearrangement of Visual Elements: Impact on Student Performance

    ERIC Educational Resources Information Center

    Yu, P.-T.; Wang, B.-Y.; Su, M.-H.

    2015-01-01

    The primary goal of this study is to create and test a lecture-capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the…

  17. Erasable photoinduced change of carrier density and coherence lengths in oxygen-deficient YBa 2Cu 3O x

    NASA Astrophysics Data System (ADS)

    Göb, W.; Lang, W.; Markowitsch, W.; Schlosser, V.; Kula, W.; Soblewski, Roman

    1995-11-01

    We report on the persistent and erasable photoinduced change of normal-state transport and superconducting properties of oxygen-deficient YBa 2Cu 3O 6.6 thin films. After illumination with white light for several hours at 150K, a decrease of the electrical resistivity, an increase of the number of mobile holes, and a change of the magnetoresistance caused by superconducting order-parameter fluctuations, were observed. From the latter measurement, we find a photoinduced enhancement of the superconducting coherence lengths in both in-plane and out-of-plane directions.

  18. Preparation of TiO2 thin films using water-soluble titanium complexes and their photoinduced properties.

    PubMed

    Katsumata, Ken-ichi; Ohno, Yukiaki; Tomita, Koji; Sakai, Munetoshi; Nakajima, Akira; Kakihana, Masato; Fujishima, Akira; Matsushita, Nobuhiro; Okada, Kiyoshi

    2011-01-01

    Titanium dioxide thin films were prepared by using four water-soluble titanium complexes of titanium-lactate, tartalate, malate and salicylate complex solutions. The crystalline phases detected in the films were anatase. The surface microstructures of the four film samples were different in their grain sizes. Photocatalytic decomposition activity of the four films was almost the same, but their photoinduced hydrophilicities were different. The film prepared using titanium-salicylate complex exhibited lower hydrophilic conversion rate than the other films. Grain size and stress yielded to the film are considered to be important factors on the photoinduced hydrophilicity.

  19. Rearrangement hotspots in the sex chromosome of the Palearctic black fly Simulium bergi (Diptera, Simuliidae)

    PubMed Central

    Adler, Peter H.; Yildirim, Alparslan; Onder, Zuhal; Tasci, G. Taskin; Duzlu, Onder; Arslan, M. Ozkan; Ciloglu, Arif; Sari, Baris; Parmaksizoglu, Nilgun; Inci, Abdullah

    2016-01-01

    Abstract An extreme example of nonrandom rearrangements, especially inversion breaks, is described in the polytene chromosomes of the black fly Simulium bergi Rubtsov, 1956 from Armenia and Turkey. A total of 48 rearrangements was discovered, relative to the standard banding sequence for the subgenus Simulium Latreille, 1802. One rearrangement, an inversion (IIS-C) in the short arm of the second chromosome, was fixed. Six (12.5%) of the rearrangements were autosomal polymorphisms, and the remaining 41 (85.4%) were sex linked. More than 40 X- and Y-linked rearrangements, predominantly inversions, were clustered in the long arm of the second chromosome (IIL), representing about 15% of the total complement. The pattern conforms to a nonrandom model of chromosome breakage, perhaps associated with an underlying molecular mechanism. PMID:27551350

  20. Inverted genomic segments and complex triplication rearrangements are mediated by inverted repeats in the human genome

    PubMed Central

    Carvalho, Claudia M. B.; Ramocki, Melissa B.; Pehlivan, Davut; Franco, Luis M.; Gonzaga-Jauregui, Claudia; Fang, Ping; McCall, Alanna; Pivnick, Eniko Karman; Hines-Dowell, Stacy; Seaver, Laurie; Friehling, Linda; Lee, Sansan; Smith, Rosemarie; del Gaudio, Daniela; Withers, Marjorie; Liu, Pengfei; Cheung, Sau Wai; Belmont, John W.; Zoghbi, Huda Y.; Hastings, P. J.; Lupski, James R.

    2011-01-01

    We identified complex genomic rearrangements consisting of intermixed duplications and triplications of genomic segments at both the MECP2 and PLP1 loci. These complex rearrangements were characterized by a triplicated segment embedded within a duplication in 12 unrelated subjects. Interestingly, only two novel breakpoint junctions were generated during each rearrangement formation. Remarkably, all the complex rearrangement products share the common genomic organization duplication-inverted triplication-duplication (DUP-TRP/INV-DUP) wherein the triplicated segment is inverted and located between directly oriented duplicated genomic segments. We provide evidence that the DUP-TRP/INV-DUP structures are mediated by inverted repeats that can be separated by over 300 kb; a genomic architecture that apparently leads to susceptibility to such complex rearrangements. A similar inverted repeat mediated mechanism may underlie structural variation in many other regions of the human genome. We propose a mechanism that involves both homology driven, via inverted repeats, and microhomologous/nonhomologous events. PMID:21964572

  1. Correlating structural order with structural rearrangement in dusty plasma liquids: can structural rearrangement be predicted by static structural information?

    PubMed

    Su, Yen-Shuo; Liu, Yu-Hsuan; I, Lin

    2012-11-09

    Whether the static microstructural order information is strongly correlated with the subsequent structural rearrangement (SR) and their predicting power for SR are investigated experimentally in the quenched dusty plasma liquid with microheterogeneities. The poor local structural order is found to be a good alarm to identify the soft spot and predict the short term SR. For the site with good structural order, the persistent time for sustaining the structural memory until SR has a large mean value but a broad distribution. The deviation of the local structural order from that averaged over nearest neighbors serves as a good second alarm to further sort out the short time SR sites. It has the similar sorting power to that using the temporal fluctuation of the local structural order over a small time interval.

  2. Spectral karyotyping identifies recurrent complex rearrangements of chromosomes 8, 17, and 20 in osteosarcomas.

    PubMed

    Bayani, Jane; Zielenska, Maria; Pandita, Ajay; Al-Romaih, Khaldoun; Karaskova, Jana; Harrison, Karen; Bridge, Julia A; Sorensen, Poul; Thorner, Paul; Squire, Jeremy A

    2003-01-01

    Conventional cytogenetic studies have shown that osteosarcomas (OSs) are often highly aneuploid, with a large number of both structural and numerical chromosomal alterations. To investigate the complexity of OS karyotypes in detail, we applied spectral karyotyping (SKY) to a series of 14 primary OS tumors and four established OS cell lines. A total of 531 rearrangements were identified by SKY, of which 300 breakpoints could be assigned to a specific chromosome band. There was an average of 38.5 breakpoints identified by SKY per primary tumor. Chromosome 20 was involved in a disproportionately high number of structural rearrangements, with 38 different aberrations being detected. Chromosomal rearrangements between chromosomes 20 and 8 were evident in four tumors. FISH analysis using a 20q13 subtelomeric probe identified frequent involvement of 20q in complex structural rearrangements of OS cell lines. Characterization of the structural aberrations of chromosomes 8 and 17 by use of SKY demonstrated frequent duplication or partial gains of chromosome bands 8q23-24 and 17p11-13. Other chromosomes frequently involved in structural alteration were chromosomes 1 (47 rearrangements) and 6 (38 rearrangements). Centromeric rearrangements often involving chromosomes 1, 6, 13, 14, 17, and 20 were present. Four of the 14 primary OS tumors were characterized by nonclonal changes that included both structural and numerical alterations. In summary, OS tumors have a very high frequency of structural and numerical alterations, compounded by gross changes in ploidy. This intrinsic karyotype instability leads to a diversity of rearrangements and the acquisition of composite chromosomal rearrangements, with the highest frequency of alteration leading to gain of 8q23-24 and 17p11-13 and rearrangement of 20q. These findings suggest that specific sequences mapping to these chromosomal regions will likely have a role in the development and progression of OS.

  3. Non-invasive three-dimensional localisation of arrhythmogenic foci in Wolff-Parkinson-White syndrome and in ventricular tachycardia by radionuclide ventriculography: phase analysis of double-angulated integrated single photon emission computed tomography (SPECT).

    PubMed Central

    Weismüller, P; Clausen, M; Weller, R; Richter, P; Steinmann, J; Henze, E; Dormehl, I; Kochs, M; Adam, W E; Hombach, V

    1993-01-01

    A new tomographic technique combined with phase analysis was used to detect premature and ectopic ventricular contraction patterns in 15 patients with Wolff-Parkinson-White syndrome and during ventricular tachycardia in seven patients. Data generated by gated single-photon emission computed tomography (SPECT) were analysed by backprojection of the Fourier coefficients, double-angulation, and integration to thick slices containing the ventricles, thus allowing visualisation of the contraction patterns in three perpendicular views. The results were compared with those of catheter mapping. In nine patients with Wolff-Parkinson-White syndrome the site of initial contraction detected was identical with the site of the accessory pathway found by catheter mapping. The sites of origin of the ventricular tachycardias determined by catheter mapping were within 3 cm of the sites detected by the new technique. This new technique seems to be a promising non-invasive method for localising ectopic ventricular activity that will considerably shorten the time required for subsequent invasive procedures. Images PMID:8461217

  4. Photoinduced Enhancement of Anisotropic Charge Correlations on Triangular Lattices with Trimers

    NASA Astrophysics Data System (ADS)

    Yonemitsu, Kenji

    2017-02-01

    To explore nontrivial photoinduced modulations of charge correlations, we theoretically study photoinduced dynamics in quarter-filled extended Hubbard models with competing intersite repulsive interactions on triangular lattices with trimers, where the end points are crystallographically equivalent. The exact diagonalization method is used and the time-dependent Schrödinger equation is numerically solved during and after photoexcitation. Time-averaged double occupancy and intersite density-density correlations can be interpreted as due to effective on-site and intersite repulsive interactions, respectively, relative to transfer energies. In the case where the intersite repulsive interactions compete with each other, the anisotropy of their effective interactions can be enhanced with the help of the trimers, irrespective of whether the trimers are linear or bent. In particular, in the case where the arrangement of the trimers is close to that in α-(bis[ethylenedithio]-tetrathiafulvalene)2I3 [α-(BEDT-TTF)2I3] in the metallic phase, the effective on-site repulsion is enhanced relative to the transfer energies. The relevance of this theoretical finding to the experimentally observed optical freezing of charge motion is discussed.

  5. Photo-induced reactions in the ion-molecule complex Mg+-OCNC2H5

    NASA Astrophysics Data System (ADS)

    Sun, Ju-Long; Liu, Haichuan; Han, Ke-Li; Yang, Shihe

    2003-06-01

    Ion-molecule complexes of magnesium cation with ethyl isocyanate were produced in a laser-ablation supersonic expansion nozzle source. Photo-induced reactions in the 1:1 complexes have been studied in the spectral range of 230-410 nm. Photodissociation mass spectrometry revealed the persistent product Mg+ from nonreactive quenching throughout the entire wavelength range. As for the reactive channels, the photoproducts, Mg+OCN and C2H5+, were produced only in the blue absorption band of the complex with low yields. The action spectrum of Mg+(OCNC2H5) consists of two pronounced peaks on the red and blue sides of the Mg+ 32P←32S atomic transition. The ground state geometry of Mg+-OCNC2H5 was fully optimized at B3LYP/6-31+G** level by using GAUSSIAN 98 package. The calculated absorption spectrum of the complex using the optimized structure of its ground state agrees well with the observed action spectrum. Photofragment branching fractions of the products are almost independent of the photolysis photon energy for the 3Px,y,z excitations. The very low branching ratio of reactive products to nonreactive fragment suggests that evaporation is the main relaxation pathway in the photo-induced reactions of Mg+(OCNC2H5).

  6. Photo-induced bending in a light-activated polymer laminated composite.

    PubMed

    Mu, Xiaoming; Sowan, Nancy; Tumbic, Julia A; Bowman, Christopher N; Mather, Patrick T; Qi, H Jerry

    2015-04-07

    Light activated polymers (LAPs) have attracted increasing attention since these materials change their shape and/or behavior in response to light exposure, which serves as an instant, remote and precisely controllable stimulus that enables non-contact control of the material shape and behavior through simple variation in light intensity, wavelength and spatially controlled exposure. These features distinguish LAPs from other active polymers triggered by other stimuli such as heat, electrical field or humidity. Previous examples have resulted in demonstrations in applications such as surface patterning, photo-induced shape memory behavior, and photo-origami. However, in many of these applications, an undesirable limitation has been the requirement to apply and maintain an external load during light irradiation. In this paper, a laminated structure is introduced to provide a pre-programmed stress field, which is then used for photo-induced deformation. This laminated structure is fabricated by bonding a stretched elastomer (NOA65) sheet between two LAP layers. Releasing the elastomer causes contraction and introduces a compressive stress in the LAPs, which are relaxed optically to trigger the desired deformation. A theoretical model is developed to quantitatively examine the laminated composite system, allowing exploration of the design space and optimum design of the laminate.

  7. Photo-induced halide redistribution in organic–inorganic perovskite films

    DOE PAGES

    deQuilettes, Dane W.; Zhang, Wei; Burlakov, Victor M.; ...

    2016-05-24

    Organic-inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced 'brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging themore » same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. In conclusion, our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.« less

  8. Tailored heterojunctions for efficient thin-film organic solar cells: a photoinduced absorption study

    NASA Astrophysics Data System (ADS)

    Schueppel, R.; Schmidt, K.; Uhrich, C.; Schulze, K.; Wynands, D.; Brédas, J. L.; Maennig, B.; Pfeiffer, M.; Leo, K.; Brier, E.; Reinold, E.; Bu, H.-B.; Baeuerle, P.

    2007-09-01

    Recently, we have demonstrated an open circuit voltage of 1.0V and a power conversion efficiency of 3.4% in thin film solar cells, utilizing a new acceptor-substituted oligothiophene with an optical gap of 1.77 eV as donor and C 60 as acceptor. Stimulated by this result, we systematically study the energy and electron transfer processes taking place at the oligothiophene:fullerene heterojunction along a homologous series of these oligothiophenes. The heterojunction is modified by tuning the HOMO level using different oligothiophene chain lengths, while the LUMO level is essentially fixed by the choice of the acceptor-type end-groups (dicyanovinyl) attached to the oligothiophene. We study electron transfer at the heterojunction to C 60 using photoinduced absorption. The observed transitions are unambiguously identified by TD-DFT calculations. With increasing the effective energy gap of the donor-acceptor pair, charge carrier dissociation following the photoinduced electron transfer is eventually replaced by recombination into the triplet state, which alters the photovoltaic operation conditions. Therefore, the optimum open-circuit voltage of a solar cell is a trade-off between an efficient charge separation at the interface and a maximized effective gap. We conclude that values between 1.0 and 1.1 V for the open-circuit voltage in our solar cell devices present an optimum, as higher voltages were only achieved with concomitant losses in charge separation efficiency.

  9. Effect of natural organic matter on the photo-induced toxicity of titanium dioxide nanoparticles.

    PubMed

    Wormington, Alexis M; Coral, Jason; Alloy, Matthew M; Damarè, Carmen L; Mansfield, Charles M; Klaine, Stephen J; Bisesi, Joseph H; Roberts, Aaron P

    2016-12-07

    Nano-titanium dioxide (TiO2 ) is the most widely used form of nanoparticles in commercial industry and comes in 2 main configurations: rutile and anatase. Rutile TiO2 is used in ultraviolet (UV) screening applications, whereas anatase TiO2 crystals have a surface defect that makes them photoreactive. There are numerous reports in the literature of photo-induced toxicity to aquatic organisms following coexposure to anatase nano-TiO2 and UV. All natural freshwater contains varying amounts of natural organic matter (NOM), which can drive UV attenuation and quench reactive oxygen species (ROS) in aquatic ecosystems. The present research examined how NOM alters the photo-induced toxicity of anatase nano-TiO2 . Daphnia magna neonates were coexposed to NOM and photoexcited anatase nano-TiO2 for 48 h. Natural organic matter concentrations as low as 4 mg/L reduced anatase nano-TiO2 toxicity by nearly 100%. These concentrations of NOM attenuated UV by <10% in the exposure system. However, ROS production measured using a fluorescence assay was significantly reduced in a NOM concentration--dependent manner. Taken together, these data suggest that NOM reduces anatase nano-TiO2 toxicity via an ROS quenching mechanism and not by attenuation of UV. Environ Toxicol Chem 2016;9999:1-6. © 2016 SETAC.

  10. OPTICAL FIBRES: Photoinduced and thermal reactions involving hydrogen in high-germania-core optical fibres

    NASA Astrophysics Data System (ADS)

    Rybaltovskii, A. O.; Koltashev, V. V.; Medvedkov, O. I.; Rybaltovsky, A. A.; Sokolov, V. O.; Klyamkin, Semen N.; Plotnichenko, V. G.; Dianov, Evgenii M.

    2008-12-01

    We report a Raman scattering study of photoinduced and thermal reactions between H2 and germanosilicate optical fibres with 22 mol % and 97 mol % GeO2 in the core (F1 and F2, respectively) after H2 loading at 150 MPa (1500 atm). The mechanisms of photoreactions are investigated in a wide range of incident laser wavelengths (244, 333, 354, 361 and 514 nm). Thermal reactions are studied at 500 °C. The results indicate that the main mechanism behind the formation of hydrogen-containing defects with Raman bands at 700, 750, 2190, 3600 and 3680 cm-1 involves ≡Ge—O—Ge≡ or ≡Ge—O—Si≡ bond breaking and formation of hydride and hydroxyl species: =GeH2 (700, 750 cm-1), ≡Ge—H (2190 cm-1), ≡GeO—H (3600 cm-1) and ≡SiO—H (3680 cm-1). The key features of the reactions in the F1 and F2 fibres are analysed. In particular, photoinduced reactions give ≡Si—OH groups only in the F1 fibres, whereas the formation of germanium nanoclusters at a relatively low temperature (~500 °C) or ≡GeO—H and ≡Ge—H defects under 514-nm irradiation has only been observed in the F2 fibres.

  11. Photo-induced halide redistribution in organic-inorganic perovskite films

    NASA Astrophysics Data System (ADS)

    Dequilettes, Dane W.; Zhang, Wei; Burlakov, Victor M.; Graham, Daniel J.; Leijtens, Tomas; Osherov, Anna; Bulović, Vladimir; Snaith, Henry J.; Ginger, David S.; Stranks, Samuel D.

    2016-05-01

    Organic-inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced `brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.

  12. Effects of photoinduced toxicity of fluoranthene on amphibian embryos and larvae

    SciTech Connect

    Hatch, A.C.; Burton, G.A. Jr.

    1998-09-01

    Embryos and newly hatched larvae of three amphibian species, the spotted salamander (Ambystoma maculatum), the northern leopard frog (Rana pipiens), and the African clawed frog (Xenopus laevis), were exposed to fluoranthene and ultraviolet (UV) light in two scenarios. Embryos were exposed in a laboratory setting from an early developmental stage through hatching under artificial UV light, and newly hatched larvae were exposed outdoors in varying sunlight intensity levels. Outdoor exposures indicated greater sensitivity in the toxic response than did laboratory exposures. In the laboratory, mortality and malformation of X. laevis were the most sensitive indicators of exposure. Xenopus laevis was also the most sensitive species tested to the effects of UV light alone. Hatching success of R. pipiens was monitored outdoors and was not a useful predictive endpoint in the determination of photoinduced toxicity; however, newly hatched larvae were sensitive to the effects of photoinduced toxicity. Amybstoma maculatum and X. laevis larvae were affected by low ({micro}g/L) concentrations of fluoranthene in sunlight. These findings suggest that low levels of polycyclic aromatic hydrocarbons could be acting synergistically with environmental factors such as UV light to place young amphibians at risk.

  13. Tracking of the molecular motion in the primary event of photoinduced reactions of a phytochromobilin model.

    PubMed

    Zhuang, Xuhui; Wang, Jun; Lan, Zhenggang

    2013-12-19

    The photoinduced processes of phytochromes have received great research interest for their important biological functions. Phytochromobilin (PΦB), one of the most important phytochrome chromophores, was selected as the prototype to study its photoinduced isomerization. The nonadiabatic dynamics of PΦB from the Pr configuration in the gas phase was investigated by the surface hopping method at the OM2/MRCI level. In the excited state, isolated PΦB does not display the rotation of the two terminal five-membered rings (ring A and ring D), which is assumed to govern the Pr → Pfr process in the protein. Instead, two S1/S0 conical intersection seams (CI01α and CI01β) characterized by the rotation of the two central rings (ring B and ring C) were proven to play essential roles for the photoisomerization of PΦB in the gas phase. These two conical intersections (CI01α and CI01β) are accessible by the twisting motions of the C9-C10 and C10-C11 bonds, respectively. The CI01α and CI01β seams, instead of their minimum-energy points, are responsible for the nonadiabatic dynamics. For both channels, the trajectories may propagate forward to the isomerization products or backward to the original Pr configuration after the S1 → S0 hops.

  14. Photo-induced halide redistribution in organic–inorganic perovskite films

    SciTech Connect

    deQuilettes, Dane W.; Zhang, Wei; Burlakov, Victor M.; Graham, Daniel J.; Leijtens, Tomas; Osherov, Anna; Bulovic, Vladimir; Snaith, Henry J.; Ginger, David S.; Stranks, Samuel D.

    2016-05-24

    Organic-inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced 'brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. In conclusion, our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.

  15. Kinetics of photoinduced ordering in azo-dye films: two-state and diffusion models.

    PubMed

    Kiselev, Alexei D; Chigrinov, Vladimir G; Kwok, Hoi-Sing

    2009-07-01

    We theoretically study the kinetics of photoinduced ordering in azo-dye photoaligning layers and present the results of modeling performed using two different phenomenological approaches. A phenomenological two-state model is deduced from the master equation for the one-particle distribution functions of an ensemble of two-level molecular systems by specifying the angular redistribution probabilities and by expressing the order parameter correlation functions in terms of the order parameter tensor. Using an alternative approach that describes light-induced reorientation of azo-dye molecules in terms of a rotational Brownian motion, we formulate the two-dimensional diffusion model as the free energy Fokker-Planck equation simplified for the limiting regime of purely in-plane reorientation. The models are employed to interpret the irradiation time dependence of the absorption order parameters defined in terms of the principal extinction (absorption) coefficients. Using the exact solution to the light transmission problem for a biaxially anisotropic absorbing layer, these coefficients are extracted from the absorbance-vs-incidence angle curves measured at different irradiation doses for the probe light linearly polarized parallel and perpendicular to the plane of incidence. It is found that, in the azo-dye films, the transient photoinduced structures are biaxially anisotropic whereas the photosteady and the initial states are uniaxial.

  16. Kinetics of photoinduced ordering in azo-dye films: Two-state and diffusion models

    SciTech Connect

    Kiselev, Alexei D.; Chigrinov, Vladimir G.; Kwok, Hoi-Sing

    2009-07-15

    We theoretically study the kinetics of photoinduced ordering in azo-dye photoaligning layers and present the results of modeling performed using two different phenomenological approaches. A phenomenological two-state model is deduced from the master equation for the one-particle distribution functions of an ensemble of two-level molecular systems by specifying the angular redistribution probabilities and by expressing the order parameter correlation functions in terms of the order parameter tensor. Using an alternative approach that describes light-induced reorientation of azo-dye molecules in terms of a rotational Brownian motion, we formulate the two-dimensional diffusion model as the free energy Fokker-Planck equation simplified for the limiting regime of purely in-plane reorientation. The models are employed to interpret the irradiation time dependence of the absorption order parameters defined in terms of the principal extinction (absorption) coefficients. Using the exact solution to the light transmission problem for a biaxially anisotropic absorbing layer, these coefficients are extracted from the absorbance-vs-incidence angle curves measured at different irradiation doses for the probe light linearly polarized parallel and perpendicular to the plane of incidence. It is found that, in the azo-dye films, the transient photoinduced structures are biaxially anisotropic whereas the photosteady and the initial states are uniaxial.

  17. Photoinduced toxicity of PrF3 and LaF3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Pudovkin, M. S.; Zelenikhin, P. V.; Krasheninnikova, A. O.; Korableva, S. L.; Nizamutdinov, A. S.; Alakshin, E. M.; Semashko, V. V.; Safiullin, R. A.; Kadirov, M. K.

    2016-10-01

    PrF3 and LaF3 nanoparticles were synthesized by the hydrothermal method. The size distribution of these nanoparticles in the colloidal solution produced was studied by photon correlation spectroscopy. The mean diameter of the nanoparticles was 42 ± 1 nm. During the study of the toxicity of the nanoparticles, the mixture of a colloidal solution of the nanoparticles with cells to be studied was irradiated by 30-mW continuous lasers at wavelengths of 532 and 473 nm. The concentration of salmonella cells in normal saline was 106 cell/mL, while that of nanoparticles was 0.1 g/L. The cell survival percentage was 39, 34, and 20% for the irradiation times of 5, 10, and 15 min, respectively, at an optimal laser radiation power density of 0.4 W/cm at a wavelength of 532 nm. It was ascertained that LaF3 nanoparticles do not possess the property of photoinduced toxicity and the apoptosing effect. Moreover, the property of photoinduced toxicity is not shared by microparticles, in contrast to nanoparticles.

  18. Photo-induced halide redistribution in organic–inorganic perovskite films

    PubMed Central

    deQuilettes, Dane W.; Zhang, Wei; Burlakov, Victor M.; Graham, Daniel J.; Leijtens, Tomas; Osherov, Anna; Bulović, Vladimir; Snaith, Henry J.; Ginger, David S.; Stranks, Samuel D.

    2016-01-01

    Organic–inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced ‘brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance. PMID:27216703

  19. Crystallinity effects on scaling properties of photoinduced modes in silver nanoprisms

    SciTech Connect

    Ng, Ming-Yaw; Ho, I-Lin; Chang, Yia-Chung

    2015-02-21

    The crystallinity effects on scaling properties of photoinduced modes in crystalline silver nanoprisms with C{sub 3v} symmetry are studied using a realistic atomistic model and group theory. Among all vibrational modes, photoinduced modes can be identified as those vibrational modes which possess larger in-phase radial atomic displacement and can be projected out by the projected density of states method. We found that the properties of vibrations in silver nanoprisms strongly depend on the particle’s aspect ratio (bisector length over thickness). By considering crystallinity of silver nanoprisms, the dominant modes with the in-plane oscillation become several closely spaced modes, and become obvious for nanoprisms with a smaller aspect ratio. The oscillation spectra show that the dominant planar modes are insensitive to thickness change. On the contrary, the atomic displacements show significantly different patterns for nanoprisms of different thicknesses. We also found that, for nanoprisms with same aspect ratio that is larger than 4, the vibrational properties of dominant modes exhibit scaling similarity. By using a simple linear transformation, the vibration frequencies for large-sized nanoprisms of aspect ratio 6 can be obtained by a corresponding scaling factor. The calculated results are in good agreement with experimental data.

  20. Quantification of photoinduced order increase in liquid crystals with naphthopyran guests

    NASA Astrophysics Data System (ADS)

    Rumi, Mariacristina; Cazzell, Seth A.; Kosa, Tamas; Sukhomlinova, Ludmila; Taheri, Bahman; White, Timothy J.; Bunning, Timothy J.

    2016-03-01

    Photoinduced order-increasing phase transitions can occur in dye-liquid crystal mixtures when the photoproduct of the excitation of the dye molecules is more compatible with the liquid crystalline medium than the initial dye species. A detailed investigation of the photoinduced changes of the phase behavior and optical properties of mixtures of liquid crystals with naphthopyran guests upon exposure to light at 365 nm is presented here. In these guest-host systems, the nematic-to-isotropic phase transition temperature is increased upon irradiation. We show that the nematic range can be extended up to 2.9 °C by illumination in 5CB (4 -n -pentyl-4'-cyanobiphenyl) liquid crystal mixtures. The order parameter is significantly increased by illumination at all temperatures within the nematic range and the changes are larger at higher concentrations of the guests. In particular, the illuminated guest-host mixtures exhibit order parameters close to those of the neat liquid crystal host at the same temperature relative to the clearing point. An improved understanding of the photophysical processes taking place at the molecular level in these material systems can inform the design of photoresponsive materials and enhance their potential utility in optical or photonic devices.

  1. Detection of ALK rearrangements in lung cancer patients using a homebrew PCR assay.

    PubMed

    Yu, Hui; Chang, JianHua; Liu, Fang; Wang, Qifeng; Lu, YongMing; Zhang, ZhuanXu; Shen, Jiabing; Zhai, Qing; Meng, Xia; Wang, Jialei; Ye, Xun

    2017-01-31

    Lung cancer patients with anaplastic lymphoma kinase (ALK) rearrangements are candidates for targeted therapeutics. However, patients must be tested with a companion diagnostic assay to realize their ALK rearrangement status. We analyzed the publicly available E-GEOD-31210 microarray dataset and identified a non-coding RNA, sweyjawbu, which is strongly associated with ALK rearrangements. We validated these results using quantitative real-time PCR in an independent cohort consisting of 4 cell lines and 83 clinical samples. We could differentiate between ALK rearrangement-positive and -negative lung cancer samples by comparing sweyjawbu expression. Additionally, ALK rearrangement status was determined by comparing the expression of the 5' and 3' regions of the ALK transcript or by detecting known ALK hybrid subtypes. Thus, using our homebrew PCR assay, we were able to accurately detect ALK rearrangements, which could be used for diagnostic screening of lung cancer patients. The prototype could potentially be transferred to an automatic multiplex PCR platform (FilmArray) to differentiate between ALK rearrangement-positive and -negative patients in point-of-care settings.

  2. The potential of clofarabine in MLL-rearranged infant acute lymphoblastic leukaemia.

    PubMed

    Stumpel, Dominique J P M; Schneider, Pauline; Pieters, Rob; Stam, Ronald W

    2015-09-01

    MLL-rearranged acute lymphoblastic leukaemia (ALL) in infants is the most difficult-to-treat type of childhood ALL, displaying a chemotherapy-resistant phenotype, and unique histone modifications, gene expression signatures and DNA methylation patterns. MLL-rearranged infant ALL responds remarkably well to nucleoside analogue drugs in vitro, such as cytarabine and cladribine, and to the demethylating agents decitabine and zebularine as measured by cytotoxicity assays. These observations led to the inclusion of cytarabine into the treatment regimens currently used for infants with ALL. However, survival chances for infants with MLL-rearranged ALL do still not exceed 30-40%. Here we explored the in vitro potential of the novel nucleoside analogue clofarabine for MLL-rearranged infant ALL. Therefore we used both cell line models as well as primary patient cells. Compared with other nucleoside analogues, clofarabine effectively targeted primary MLL-rearranged infant ALL cells at the lowest concentrations, with median LC50 values of ∼25 nM. Interestingly, clofarabine displayed synergistic cytotoxic effects in combination with cytarabine. Furthermore, at concentrations of 5-10nM clofarabine induced demethylation of the promoter region of the tumour suppressor gene FHIT (Fragile Histidine Triad), a gene typically hypermethylated in MLL-rearranged ALL. Demethylation of the FHIT promoter region was accompanied by subtle re-expression of this gene both at the mRNA and protein level. We conclude that clofarabine is an interesting candidate for further studies in MLL-rearranged ALL in infants.

  3. BRCA1 and BRCA2 rearrangements in Brazilian individuals with Hereditary Breast and Ovarian Cancer Syndrome.

    PubMed

    Ewald, Ingrid Petroni; Cossio, Silvia Liliana; Palmero, Edenir Inez; Pinheiro, Manuela; Nascimento, Ivana Lucia de Oliveira; Machado, Taisa Manuela Bonfim; Sandes, Kiyoko Abe; Toralles, Betânia; Garicochea, Bernardo; Izetti, Patricia; Pereira, Maria Luiza Saraiva; Bock, Hugo; Vargas, Fernando Regla; Moreira, Miguel Ângelo Martins; Peixoto, Ana; Teixeira, Manuel R; Ashton-Prolla, Patricia

    2016-01-01

    Approximately 5-10% of breast cancers are caused by germline mutations in high penetrance predisposition genes. Among these, BRCA1 and BRCA2, which are associated with the Hereditary Breast and Ovarian Cancer (HBOC) syndrome, are the most frequently affected genes. Recent studies confirm that gene rearrangements, especially in BRCA1, are responsible for a significant proportion of mutations in certain populations. In this study we determined the prevalence of BRCA rearrangements in 145 unrelated Brazilian individuals at risk for HBOC syndrome who had not been previously tested for BRCA mutations. Using Multiplex Ligation-dependent Probe Amplification (MLPA) and a specific PCR-based protocol to identify a Portuguese founder BRCA2 mutation, we identified two (1,4%) individuals with germline BRCA1 rearrangements (c.547+240_5193+178del and c.4675+467_5075-990del) and three probands with the c.156_157insAlu founder BRCA2 rearrangement. Furthermore, two families with false positive MLPA results were shown to carry a deleterious point mutation at the probe binding site. This study comprises the largest Brazilian series of HBOC families tested for BRCA1 and BRCA2 rearrangements to date and includes patients from three regions of the country. The overall observed rearrangement frequency of 3.44% indicates that rearrangements are relatively uncommon in the admixed population of Brazil.

  4. BRCA1 and BRCA2 rearrangements in Brazilian individuals with Hereditary Breast and Ovarian Cancer Syndrome

    PubMed Central

    Ewald, Ingrid Petroni; Cossio, Silvia Liliana; Palmero, Edenir Inez; Pinheiro, Manuela; Nascimento, Ivana Lucia de Oliveira; Machado, Taisa Manuela Bonfim; Sandes, Kiyoko Abe; Toralles, Betânia; Garicochea, Bernardo; Izetti, Patricia; Pereira, Maria Luiza Saraiva; Bock, Hugo; Vargas, Fernando Regla; Moreira, Miguel Ângelo Martins; Peixoto, Ana; Teixeira, Manuel R.; Ashton-Prolla, Patricia

    2016-01-01

    Abstract Approximately 5-10% of breast cancers are caused by germline mutations in high penetrance predisposition genes. Among these, BRCA1 and BRCA2, which are associated with the Hereditary Breast and Ovarian Cancer (HBOC) syndrome, are the most frequently affected genes. Recent studies confirm that gene rearrangements, especially in BRCA1, are responsible for a significant proportion of mutations in certain populations. In this study we determined the prevalence of BRCA rearrangements in 145 unrelated Brazilian individuals at risk for HBOC syndrome who had not been previously tested for BRCA mutations. Using Multiplex Ligation-dependent Probe Amplification (MLPA) and a specific PCR-based protocol to identify a Portuguese founder BRCA2 mutation, we identified two (1,4%) individuals with germline BRCA1 rearrangements (c.547+240_5193+178del and c.4675+467_5075-990del) and three probands with the c.156_157insAlu founder BRCA2 rearrangement. Furthermore, two families with false positive MLPA results were shown to carry a deleterious point mutation at the probe binding site. This study comprises the largest Brazilian series of HBOC families tested for BRCA1 and BRCA2 rearrangements to date and includes patients from three regions of the country. The overall observed rearrangement frequency of 3.44% indicates that rearrangements are relatively uncommon in the admixed population of Brazil. PMID:27303907

  5. CASSCF Computational Study of Pseudopericyclic Character in Electrocyclic Rearrangements Involving Heteroatoms.

    PubMed

    Bierzynski, Irena R; Settle, Cassandra A; Kreiman, Henry W; Duncan, James A

    2016-01-15

    The Complete Active Space Self-Consistent Field (CASSCF) computational method, with the 6-31G* basis set, was used to examine six electrocyclic rearrangements, each involving a 1,2,4,6-heptatetraene skeleton with two variously located oxygen and/or nitrogen heteroatoms, as a way to determine which, if any, are pseudopericyclic as opposed to pericyclic. Primarily through the close examination of the active space orbitals, but also considering transition structure geometries and activation energies, it was concluded that rearrangements 3 → 4, 5 → 6, 7 → 8, and 9 → 10 are pseudopericyclic with two orbital disconnections each, whereas the 13 → 14 and 15 → 16 rearrangements are pericyclic. Our conclusions agreed with those of others in two of the four cases that had been studied previously by density functional theory (3 → 4 and 7 → 8) but ran contrary to the previous conclusions that the 5 → 6 rearrangement is pericyclic and that the 15 → 16 rearrangement is pseudopericyclic. Our results are also compared and contrasted to previous similar ones of ours involving the 3 → 4 electrocyclization (essentially pericyclic), the 11 → 12 [3,3] sigmatropic rearrangement (pseudopericyclic), and similar [3,3] sigmatropic rearrangements (all pericyclic), and detailed rationales for these latest results are provided.

  6. Directional photoinduced electron transfer in paraquat silicate thin films containing entrapped ruthenium(II)-tris(bathophenanthroline-disulfonate).

    PubMed

    Trammell, Scott A; Tsoi, Stanislav; Martin, Brett; Melde, Brian J; Moore, Martin M; Dressick, Walter J

    2011-10-28

    We have demonstrated directional photoinduced electron transfer in paraquat silicate thin films containing entrapped ruthenium(II)-tris(bathophenanthroline-disulfonate (RuBPS). The films were made by electrochemically-induced hydrolysis of a silane analogue of paraquat with ruthenium(II)-tris(bathophenanthroline-disulfonate as its ion pair.

  7. Photo-induced hydrogen production in a helical peptide incorporating a [FeFe] hydrogenase active site mimic.

    PubMed

    Roy, Anindya; Madden, Christopher; Ghirlanda, Giovanna

    2012-10-11

    There is growing interest in the development of hydrogenase mimics for solar fuel production. Here, we present a bioinspired mimic designed by anchoring a diiron hexacarbonyl cluster to a model helical peptide via an artificial dithiol amino acid. The [FeFe]-peptide complex catalyses photo-induced production of hydrogen in water.

  8. Photoinduced Graft-Polymerization of Acrylic Acid on Polyethylene and Polypropylene Surfaces: Comparative Study Using IR-ATR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gorbachev, A. A.; Tretinnikov, O. N.; Shkrabatovskaya, L. V.; Prikhodchenko, L. K.

    2014-11-01

    Photoinduced graft-polymerization of acrylic acid on the surface of polyethylene and polypropylene films containing a photoinitiator pre-adsorbed from a thin layer of non-de-aerated aqueous monomer solution was investigated. Data about the monomer conversion and grafting depth as functions of the UV irradiation time and polymer nature were obtained using IR-ATR spectroscopy.

  9. Facile Synthesis of Stapled, Structurally Reinforced Peptide Helices via A Photoinduced Intramolecular 1,3-Dipolar Cycloaddition Reaction†

    PubMed Central

    Madden, Michael M.; Vera, Claudia I. Rivera; Song, Wenjiao; Lin, Qing

    2009-01-01

    We report the first use of a photoinduced 1,3-dipolar cycloaddition reaction in “stapling” peptide side chains to reinforce a model peptide helical structure with moderate to excellent yields. The resulting pyrazoline “staplers” exhibit unique fluorescence useful in a cell permeability study. PMID:19753366

  10. Time-resolved x-ray absorption spectroscopy of photoinduced insulator-metal transition in a colossal magnetoresistive manganite

    SciTech Connect

    Rini, M.; Tobey, R.; Wall, S.; Zhu, Y.; Tomioka, Y.; Tokura, Y.; Cavalleri, A.; Schoenlein, R.W.

    2008-08-01

    We studied the ultrafast insulator-metal transition in a manganite by means of picosecond X-ray absorption at the O K- and Mn L-edges, probing photoinduced changes in O-2p and Mn-3d electronic states near the Fermi level.

  11. Towards efficient photoinduced charge separation in carbon nanodots and TiO2 composites in the visible region.

    PubMed

    Sun, Mingye; Qu, Songnan; Ji, Wenyu; Jing, Pengtao; Li, Di; Qin, Li; Cao, Junsheng; Zhang, Hong; Zhao, Jialong; Shen, Dezhen

    2015-03-28

    In this work, photoinduced charge separation behaviors in non-long-chain-molecule-functionalized carbon nanodots (CDs) with visible intrinsic absorption (CDs-V) and TiO2 composites were investigated. Efficient photoinduced electron injection from CDs-V to TiO2 with a rate of 8.8 × 10(8) s(-1) and efficiency of 91% was achieved in the CDs-V/TiO2 composites. The CDs-V/TiO2 composites exhibited excellent photocatalytic activity under visible light irradiation, superior to pure TiO2 and the CDs with the main absorption band in the ultraviolet region and TiO2 composites, which indicated that visible photoinduced electrons and holes in such CDs-V/TiO2 composites could be effectively separated. The incident photon-to-current conversion efficiency (IPCE) results for the CD-sensitized TiO2 solar cells also agreed with efficient photoinduced charge separation between CDs-V and the TiO2 electrode in the visible range. These results demonstrate that non-long-chain-molecule-functionlized CDs with a visible intrinsic absorption band could be appropriate candidates for photosensitizers and offer a new possibility for the development of a well performing CD-based photovoltaic system.

  12. Mechanistic insights into the photoinduced charge carrier dynamics of BiOBr/CdS nanosheet heterojunctions for photovoltaic application.

    PubMed

    Jia, Huimin; Zhang, Beibei; He, Weiwei; Xiang, Yong; Zheng, Zhi

    2017-03-02

    The rational design of high performance hetero-structure photovoltaic devices requires a full understanding of the photoinduced charge transfer mechanism and kinetics at the interface of heterojunctions. In this paper, we intelligently fabricated p-BiOBr/n-CdS heterojunctions with perfect nanosheet arrays by using a facile successive ionic layer adsorption and reaction and chemical bath deposition methods at low temperature. A BiOBr/CdS heterojunction based solar cell has been fabricated which exhibited enhanced photovoltaic responses. Assisted by the surface photovoltage (SPV), transient photovoltage (TPV) and Kelvin probe technique, the photoinduced charge transfer dynamics on the BiOBr nanosheet and p-BiOBr/n-CdS interface were systematically investigated. It was found that the BiOBr/CdS nanosheet array heterojunctions were more efficient in facilitating charge carrier separation than both bare BiOBr and CdS films. The mechanism underlying the photoinduced charge carrier transfer behaviour was unravelled by allying the energy band of BiOBr/CdS p-n junctions from both the interfacial electric field and surface electric field. In addition, the CdS loading thickness in the p-BiOBr/n-CdS heterojunction and the incident wavelength affected greatly the transfer behavior of photoinduced charges, which was of great value for design of photovoltaic devices.

  13. PHOTO-INDUCED POLYCYCLIC AROMATIC HYDROCARBON TOXIC POTENTIALS OF NEAR SHORE LARVAL FISH HABITAT IN THE GREAT LAKES, USA

    EPA Science Inventory

    Photo-induced toxicity (PIT) of polycyclic aromatic hydrocarbons (PAH) has been documented in laboratory studies for both invertebrate and vertebrate aquatic organisms. PIT has not been verified in field studies for larval fish to date. Filtered water samples and larval fish were...

  14. Kinetics of homoallylic/homobenzylic rearrangement reactions under combustion conditions.

    PubMed

    Wang, Zhaohui; Zhang, Lidong; Zhang, Feng

    2014-08-28

    Homoallylic/homobenzylic radicals refer to typical radicals with the radical site located at the β position from the vinyl/phenyl group. These radicals are largely involved in combustion systems, such as the pyrolysis or oxidation of alkenes, cycloalkanes, and aromatics. The 1,2-vinyl/phenyl migration via two steps (cyclization/fission) is a peculiar reaction type for the homoallylic/homobenzylic radicals, entitled homoallylic/homobenzylic rearrangement, which has been studied by theoretical calculations including the Hirshfeld atomic charge analysis in the present work. With the help of rate constant calculations, the competition between this reaction channel and other possible pathways under combustion temperatures (500-2000 K) were evaluated. Analogous 1,3- and 1,4-vinyl/phenyl migration reactions for similar radicals with the radical sites located at the γ and δ positions from the vinyl/phenyl group were also computed. The results indicate that the 1,2-vinyl/phenyl migration is particularly important for the kinetics of unimolecular reactions of homoallylic radicals under 1500 K; nevertheless, it still has noticeable contribution at higher temperature. For those radicals with the radical site at the γ or δ positions, the respective 1,3- or 1,4-vinyl/phenyl migration channel plays an insignificant role under combustion conditions.

  15. Centrosome centering and decentering by microtubule network rearrangement

    PubMed Central

    Letort, Gaëlle; Nedelec, Francois; Blanchoin, Laurent; Théry, Manuel

    2016-01-01

    The centrosome is positioned at the cell center by pushing and pulling forces transmitted by microtubules (MTs). Centrosome decentering is often considered to result from asymmetric, cortical pulling forces exerted in particular by molecular motors on MTs and controlled by external cues affecting the cell cortex locally. Here we used numerical simulations to investigate the possibility that it could equally result from the redistribution of pushing forces due to a reorientation of MTs. We first showed that MT gliding along cell edges and pivoting around the centrosome regulate MT rearrangement and thereby direct the spatial distribution of pushing forces, whereas the number, dynamics, and stiffness of MTs determine the magnitude of these forces. By modulating these parameters, we identified different regimes, involving both pushing and pulling forces, characterized by robust centrosome centering, robust off-centering, or “reactive” positioning. In the last-named conditions, weak asymmetric cues can induce a misbalance of pushing and pulling forces, resulting in an abrupt transition from a centered to an off-centered position. Taken together, these results point to the central role played by the configuration of the MTs on the distribution of pushing forces that position the centrosome. We suggest that asymmetric external cues should not be seen as direct driver of centrosome decentering and cell polarization but instead as inducers of an effective reorganization of the MT network, fostering centrosome motion to the cell periphery. PMID:27440925

  16. Effects of structural rearrangements on sorption capacity of coals

    SciTech Connect

    Romanov, Vyacheslav; Soong, Yee; Warzinski, R.P.; Lynn, R.J.

    2006-09-01

    Recently, the problems in practical application of experimental data and modeling to the sequestration of carbon dioxide in coal seams and the concurrent enhanced coalbed methane (ECBM) recovery have underscored the need for new approaches that take into account the ability of coal for structural rearrangements. Areas of interest include plasticization of coal due to CO2 dissolution, the effect of coal swelling on estimation of the capacity of a coal-seam to adsorb CO2 (adsorption isotherm), and the stability of the CO2 saturated phase once formed, especially with respect to how it might be affected by changes in the post-sequestration environment (environmental effects). Coals are organic macromolecular systems well known to imbibe organic liquids and carbon dioxide. CO2 dissolves in coals and swells them. The problems become more prominent in the region of supercritical CO2. We investigated the effects of moisture content and pressure cycling history on temporal changes in the coal sorptive capacity for a set of Argonne premium coals. The samples were tested as received, dried at 80oC for 36 hours, and moisture equilibrated at 96-97% RH and 30oC for 48 hours. The powders were compared to core samples. Additionally, plasticization of coal powders was studied by high pressure dilatometer.

  17. Centrosome centering and decentering by microtubule network rearrangement.

    PubMed

    Letort, Gaëlle; Nedelec, Francois; Blanchoin, Laurent; Théry, Manuel

    2016-09-15

    The centrosome is positioned at the cell center by pushing and pulling forces transmitted by microtubules (MTs). Centrosome decentering is often considered to result from asymmetric, cortical pulling forces exerted in particular by molecular motors on MTs and controlled by external cues affecting the cell cortex locally. Here we used numerical simulations to investigate the possibility that it could equally result from the redistribution of pushing forces due to a reorientation of MTs. We first showed that MT gliding along cell edges and pivoting around the centrosome regulate MT rearrangement and thereby direct the spatial distribution of pushing forces, whereas the number, dynamics, and stiffness of MTs determine the magnitude of these forces. By modulating these parameters, we identified different regimes, involving both pushing and pulling forces, characterized by robust centrosome centering, robust off-centering, or "reactive" positioning. In the last-named conditions, weak asymmetric cues can induce a misbalance of pushing and pulling forces, resulting in an abrupt transition from a centered to an off-centered position. Taken together, these results point to the central role played by the configuration of the MTs on the distribution of pushing forces that position the centrosome. We suggest that asymmetric external cues should not be seen as direct driver of centrosome decentering and cell polarization but instead as inducers of an effective reorganization of the MT network, fostering centrosome motion to the cell periphery.

  18. Ferrier rearrangement promoted by an electrochemically generated zirconium catalyst.

    PubMed

    Stevanović, Dragana; Pejović, Anka; Damljanović, Ivan; Minić, Aleksandra; Bogdanović, Goran A; Vukićević, Mirjana; Radulović, Niko S; Vukićević, Rastko D

    2015-04-30

    In situ generated zirconium catalyst from a sacrificial zirconium anode was successfully applied to promote Ferrier rearrangement of 3,4,5-tri-O-acetyl-D-glucal and 6-deoxy-3,4-di-O-acetyl-L-glucal (3,4-di-O-acetyl-L-rhamnal) in the presence of three thiols and eleven thiophenols as nucleophiles. A simple constant current electrolysis (20 mA, 0.4 F mol(-1)) of an acetonitrile solution of lithium perchlorate (0.1 M) containing the corresponding glycal and S-nucleophiles, using a zirconium anode and a platinum cathode resulted in the successful synthesis of the corresponding 2,3-unsaturated peracetylated thioglycosides (with an average anomer ratio α/β=4.129 in the case of peracetylated D-glucal and 8.740 in the case of L-rhamnal). The same procedure proved to be appropriate in synthesizing dihydropyran derivatives ('C-glycosides') using allyltrimethylsilane as the nucleophile (only 'α-anomers' were obtained). All new compounds were fully characterized by spectral data, whereas single-crystal X-ray analysis was performed for two thioglycosides.

  19. Complex Chromosomal Rearrangements Induced in Vivo by Heavy Ions

    NASA Technical Reports Server (NTRS)

    Durante, M.; Ando, K.; Furusawa, G.; Obe, G.; George, K.; Cucinotta, F. A.

    2004-01-01

    It has been suggested that the ratio complex/simple exchanges can be used as a biomarker of exposure to high-LET radiation. We tested this hypothesis in vivo, by considering data from several studies that measured complex exchanges in peripheral blood from humans exposed to mixed fields of low- and high-LET radiation. In particular, we studied data from astronauts involved in long-term missions in low-Earth-orbit, and uterus cancer patients treated with accelerated carbon ions. Data from two studies of chromosomal aberrations in astronauts used blood samples obtained before and after space flight, and a third study used blood samples from patients before and after radiotherapy course. Similar methods were used in each study, where lymphocytes were stimulated to grow in vitro, and collected after incubation in either colcemid or calyculin A. Slides were painted with whole-chromosome DNA fluorescent probes (FISH), and complex and simple chromosome exchanges in the painted genome were classified separately. Complex-type exchanges were observed at low frequencies in control subjects, and in our test subjects before the treatment. No statistically significant increase in the yield of complex-type exchanges was induced by the space flight. Radiation therapy induced a high fraction of complex exchanges, but no significant differences could be detected between patients treated with accelerated carbon ions or X-rays. Complex chromosomal rearrangements do not represent a practical biomarker of radiation quality in our test subjects. Copyright 2003 S. Karger AG, Basel.

  20. Order and disorder control the functional rearrangement of influenza hemagglutinin.

    PubMed

    Lin, Xingcheng; Eddy, Nathanial R; Noel, Jeffrey K; Whitford, Paul C; Wang, Qinghua; Ma, Jianpeng; Onuchic, José N

    2014-08-19

    Influenza hemagglutinin (HA), a homotrimeric glycoprotein crucial for membrane fusion, undergoes a large-scale structural rearrangement during viral invasion. X-ray crystallography has shown that the pre- and postfusion configurations of HA2, the membrane-fusion subunit of HA, have disparate secondary, tertiary, and quaternary structures, where some regions are displaced by more than 100 Å. To explore structural dynamics during the conformational transition, we studied simulations of a minimally frustrated model based on energy landscape theory. The model combines structural information from both the pre- and postfusion crystallographic configurations of HA2. Rather than a downhill drive toward formation of the central coiled-coil, we discovered an order-disorder transition early in the conformational change as the mechanism for the release of the fusion peptides from their burial sites in the prefusion crystal structure. This disorder quickly leads to a metastable intermediate with a broken threefold symmetry. Finally, kinetic competition between the formation of the extended coiled-coil and C-terminal melting results in two routes from this intermediate to the postfusion structure. Our study reiterates the roles that cracking and disorder can play in functional molecular motions, in contrast to the downhill mechanical interpretations of the "spring-loaded" model proposed for the HA2 conformational transition.

  1. Rearrangement of beta-amino alcohols and application to the synthesis of biologically active compounds.

    PubMed

    Cossy, Janine; Pardo, Domingo Gomez; Dumas, Cécile; Mirguet, Olivier; Déchamps, Ingrid; Métro, Thomas-Xavier; Burger, Benjamin; Roudeau, Rémi; Appenzeller, Jérôme; Cochi, Anne

    2009-10-01

    Beta-amino alcohols derived from natural amino acids have been used extensively as a powerful source of chirality. Transformation of the hydroxy group of these beta-amino alcohols into a good leaving group, by using trifluoroacetic anhydride, led to rearranged beta-amino alcohols in good yields and with high enantiomeric excesses. This rearrangement has allowed the transformation of substituted prolinols to substituted 3-hydroxypiperidines and linear beta-amino alcohols, issued from natural amino acids, to rearranged beta-amino alcohols.

  2. Development of the scope of a co-mediated O-->C rearrangement reaction.

    PubMed

    Meek, Simon J; Pradaux, Fabienne; Carbery, David R; Demont, Emmanuel H; Harrity, Joseph P A

    2005-11-25

    [reaction: see text] In this paper we describe an Al-promoted, Co-mediated O-->C rearrangement reaction of cyclic enol ethers. This process delivers functionalized cyclohexanones with good to excellent levels of diastereocontrol, whereby the product stereochemistry is dependent on the E/Z-stereochemistry of the starting enol ether. The rearrangement process also permits access to highly substituted alpha-spirocyclic cyclohexanones as well as cyclopentanones. The latter rearrangement appears to proceed via an unusual 5-(enolendo)-exo-trig cyclization process.

  3. Transient electronic structure of the photoinduced phase of Pr0.7Ca0.3MnO3 probed with soft x-ray pulses

    SciTech Connect

    Rini, M.; Zhu, Y.; Wall, S.; Tobey, R. I.; Ehrke, H.; Garl, T.; Freeland, J. W.; Tomioka, Y.; Tokura, Y.; Cavalleri, A.; Schoenlein, R. W.

    2009-04-01

    We use time-resolved x-ray absorption near-edge structure spectroscopy to investigate the electronic dynamics associated with the photoinduced insulator-to-metal phase transition in the colossal magnetoresistive manganite Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3}. Absorption changes at the O K and Mn L edges directly monitor the evolution of the density of unoccupied states in the transient photoinduced phase. We show that the electronic structure of the photoinduced phase is remarkably similar to that of the ferromagnetic metallic phase reached in related manganites upon cooling below the Curie temperature.

  4. Photoinduced processes in hybrid structures on the basis of TiO2 nanoparticles and CdSe/ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Kolesova, E. P.; Orlova, A. O.; Maslov, V. G.; Gun'ko, Yu. K.; Cleary, O.; Baranov, A. V.; Fedorov, A. V.

    2017-01-01

    The morphology of and photoinduced changes in the luminescent properties of hybrid structures on the basis of TiO2 nanoparticles and CdSe/ZnS quantum dots are studied. It is established that the morphology of the structures depends on the method of their formation and the type of stabilizer of the CdSe/ZnS surface. It is shown that a photoinduced decrease in the efficiency of nonradiative relaxation of the excitation in the quantum dots leads to an increase in the quantum yield of their luminescence and an increase in the efficiency of photoinduced charge transfer in hybrid structures.

  5. Aromatic Claisen Rearrangements of O-prenylated tyrosine and model prenyl aryl ethers: Computational study of the role of water on acceleration of Claisen rearrangements.

    PubMed

    Osuna, Sílvia; Kim, Seonah; Bollot, Guillaume; Houk, K N

    2013-05-01

    LynF, an enzyme from the TruF family, O-prenylates tyrosines in proteins; subsequent Claisen rearrangements give C-prenylated tyrosine products. These reactions in tyrosines and model phenolic systems have been explored with DFT and SCS-MP2 calculations. Various ab initio benchmarks have been computed (CBS-QB3, MP2, SCS-MP2) to examine the accuracy of commonly used density functionals, such as B3LYP and M06-2X. Solvent effects from water were considered using implicit and explicit models. Studies of the ortho-C-prenylation and Claisen rearrangement of tyrosine, and the Claisen rearrangement of α,α-dimethylallyl (prenyl) coumaryl ether establish the energetics of these reactions in the gas phase and in aqueous solution.

  6. Aromatic Claisen Rearrangements of O-prenylated tyrosine and model prenyl aryl ethers: Computational study of the role of water on acceleration of Claisen rearrangements

    PubMed Central

    Osuna, Sílvia; Kim, Seonah; Bollot, Guillaume; Houk, K. N.

    2013-01-01

    LynF, an enzyme from the TruF family, O-prenylates tyrosines in proteins; subsequent Claisen rearrangements give C-prenylated tyrosine products. These reactions in tyrosines and model phenolic systems have been explored with DFT and SCS-MP2 calculations. Various ab initio benchmarks have been computed (CBS-QB3, MP2, SCS-MP2) to examine the accuracy of commonly used density functionals, such as B3LYP and M06-2X. Solvent effects from water were considered using implicit and explicit models. Studies of the ortho-C-prenylation and Claisen rearrangement of tyrosine, and the Claisen rearrangement of α,α-dimethylallyl (prenyl) coumaryl ether establish the energetics of these reactions in the gas phase and in aqueous solution. PMID:24376368

  7. Complex structural rearrangement features suggesting chromoanagenesis mechanism in a case of 1p36 deletion syndrome.

    PubMed

    Zanardo, Évelin Aline; Piazzon, Flavia Balbo; Dutra, Roberta Lelis; Dias, Alexandre Torchio; Montenegro, Marília Moreira; Novo-Filho, Gil Monteiro; Costa, Thaís Virgínia Moura Machado; Nascimento, Amom Mendes; Kim, Chong Ae; Kulikowski, Leslie Domenici

    2014-12-01

    Genome rearrangements are caused by the erroneous repair of DNA double-strand breaks, leading to several alterations that result in loss or gain of the structural genomic of a dosage-sensitive genes. However, the mechanisms that promote the complexity of rearrangements of congenital or developmental defects in human disease are unclear. The investigation of complex genomic abnormalities could help to elucidate the mechanisms and causes for the formation and facilitate the understanding of congenital or developmental defects in human disease. We here report one case of a patient with atypical clinical features of the 1p36 syndrome and the use of cytogenomic techniques to characterize the genomic alterations. Analysis by multiplex ligation-dependent probe amplification and array revealed a complex rearrangement in the 1p36.3 region with deletions and duplication interspaced by normal sequences. We also suggest that chromoanagenesis could be a possible mechanism involved in the repair and stabilization of this rearrangement.

  8. Synthesis of gamma,delta-unsaturated glycolic acids via sequenced brook and Ireland--claisen rearrangements.

    PubMed

    Schmitt, Daniel C; Johnson, Jeffrey S

    2010-03-05

    Organozinc, -magnesium, and -lithium nucleophiles initiate a Brook/Ireland-Claisen rearrangement sequence of allylic silyl glyoxylates resulting in the formation of gamma,delta-unsaturated alpha-silyloxy acids.

  9. Conversion of allylic alcohols to stereodefined trisubstituted alkenes: a complementary process to the Claisen rearrangement.

    PubMed

    Belardi, Justin K; Micalizio, Glenn C

    2008-12-17

    A stereoselective method for the conversion of allylic alcohols to (Z)-trisubstituted alkenes is presented. Overall, the reaction sequence described is stereochemically complementary to related Claisen rearrangement reactions--processes that typically deliver the stereoisomeric trisubstituted alkene containing products.

  10. Enantioselective synthesis of allenamides via sulfimide [2,3]-sigmatropic rearrangement.

    PubMed

    Armstrong, Alan; Emmerson, Daniel P G

    2009-04-02

    Chiral allenamides are prepared with high levels of enantiomeric purity by [2,3]-sigmatropic rearrangement of propargylic sulfimides. The required branched propargylic sulfides are prepared by an enantioselective organocatalytic aldehyde alpha-sulfenylation followed by Corey-Fuchs alkynylation.

  11. Extending the algebraic formalism for genome rearrangements to include linear chromosomes.

    PubMed

    Feijão, Pedro; Meidanis, João

    2013-01-01

    Algebraic rearrangement theory, as introduced by Meidanis and Dias, focuses on representing the order in which genes appear in chromosomes, and applies to circular chromosomes only. By shifting our attention to genome adjacencies, we introduce the adjacency algebraic theory, extending the original algebraic theory to linear chromosomes in a very natural way, also allowing the original algebraic distance formula to be used to the general multichromosomal case, with both linear and circular chromosomes. The resulting distance, which we call algebraic distance here, is very similar to, but not quite the same as, double-cut-and-join distance. We present linear time algorithms to compute it and to sort genomes. We show how to compute the rearrangement distance from the adjacency graph, for an easier comparison with other rearrangement distances. A thorough discussion on the relationship between the chromosomal and adjacency representation is also given, and we show how all classic rearrangement operations can be modeled using the algebraic theory.

  12. Rearrangement of 5-trimethylsilylthebaine on treatment with L-selectride: an efficient synthesis of (+)-bractazonine.

    PubMed

    Chen, Weibin; Wu, Huifang; Bernard, Denzil; Metcalf, Matthew D; Deschamps, Jeffrey R; Flippen-Anderson, Judith L; MacKerell, Alexander D; Coop, Andrew

    2003-03-07

    Treatment of 5-trimethylsilylthebaine with L-Selectride gave rise to a rearrangement to 10-trimethylsilylbractazonine through migration of the phenyl group, whereas treatment of thebaine with strong Lewis acids is known to lead to a similar rearrangement through migration of the alkyl bridge to give, after reduction, (+)-neodihydrothebaine. It is suggested that the rearrangement of the alkyl group of thebaine is favored due to the formation of a tertiary benzylic cation. However, for 5-trimethylsilylthebaine, the lithium ion of L-Selectride acts as the Lewis acid and the beta-silyl effect dominates in the stabilization of any positive charge. This rearrangement provides a clear example of the greater relative migratory aptitude of phenyl groups over alkyl groups, and provides an efficient synthesis of (+)-bractazonine from thebaine.

  13. Massive genomic rearrangement acquired in a single catastrophic event during cancer development.

    PubMed

    Stephens, Philip J; Greenman, Chris D; Fu, Beiyuan; Yang, Fengtang; Bignell, Graham R; Mudie, Laura J; Pleasance, Erin D; Lau, King Wai; Beare, David; Stebbings, Lucy A; McLaren, Stuart; Lin, Meng-Lay; McBride, David J; Varela, Ignacio; Nik-Zainal, Serena; Leroy, Catherine; Jia, Mingming; Menzies, Andrew; Butler, Adam P; Teague, Jon W; Quail, Michael A; Burton, John; Swerdlow, Harold; Carter, Nigel P; Morsberger, Laura A; Iacobuzio-Donahue, Christine; Follows, George A; Green, Anthony R; Flanagan, Adrienne M; Stratton, Michael R; Futreal, P Andrew; Campbell, Peter J

    2011-01-07

    Cancer is driven by somatically acquired point mutations and chromosomal rearrangements, conventionally thought to accumulate gradually over time. Using next-generation sequencing, we characterize a phenomenon, which we term chromothripsis, whereby tens to hundreds of genomic rearrangements occur in a one-off cellular crisis. Rearrangements involving one or a few chromosomes crisscross back and forth across involved regions, generating frequent oscillations between two copy number states. These genomic hallmarks are highly improbable if rearrangements accumulate over time and instead imply that nearly all occur during a single cellular catastrophe. The stamp of chromothripsis can be seen in at least 2%-3% of all cancers, across many subtypes, and is present in ∼25% of bone cancers. We find that one, or indeed more than one, cancer-causing lesion can emerge out of the genomic crisis. This phenomenon has important implications for the origins of genomic remodeling and temporal emergence of cancer.

  14. TDDFT-MD Study on Dynamics in Photoinduced Ring Opening of Benzene

    NASA Astrophysics Data System (ADS)

    Tateyama, Yoshitaka; Miyamoto, Yoshiyuki; Oyama, Norihisa; Ohno, Takahisa

    2004-03-01

    Coupled dynamics of ions and electrons in the excited states of molecular and solid benzene is investigated on the femtosecond scale by the efficient simulation scheme recently developed for the time-dependent density functional theory. Within the π arrow π excitations, any out-of-plane motion of ions is not induced in the molecular system basically. In the solid, however, we found that large swing of the C-H bonds and subsequent twist of the carbon ring takes place, leading to sp^3-like bonding of carbon ions. This swing-to-twist motion presents a plausible mechanism underlying the photoinduced ring opening in solid benzene experimentally observed under pressure. This research is partially supported by ACT-JST, and also by FSIS and Special Coordination Funds of Ministry of Education, Culture, Sports, Science and Technology of Japanese Government.

  15. Role of coherence and delocalization in photo-induced electron transfer at organic interfaces

    PubMed Central

    Abramavicius, V.; Pranculis, V.; Melianas, A.; Inganäs, O.; Gulbinas, V.; Abramavicius, D.

    2016-01-01

    Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces. PMID:27605035

  16. Synthesis and Characterization of Coumarin-Containing Cyclic Polymer and Its Photoinduced Coupling/Dissociation.

    PubMed

    Li, Min; Fan, Wei; Hong, Chunyan; Pan, Caiyuan

    2015-12-01

    Cyclic polystyrene (PS) with a pendant coumarin group is prepared by the combination of atom transfer radical polymerization and "click" chemistry. Fluorescence resonance energy transfer process is observed in the fluorescence measurement of coumarin-containing PS, and cyclic PS exhibits stronger emission than that of its linear precursor. When cyclic PS is irradiated under UV light at λ = 365 nm, 8-shaped PS is achieved due to the dimerization of pendant coumarin group. Subsequently, 8-shaped PS can be divided into single macrocycle under UV irradiation at λ = 254 nm via the photocleavage of coumarin dimer. The photoinduced coupling and dissociation are monitored by UV/vis spectra and gel permeation chromatography (GPC).

  17. Dependence of photoinduced bending behavior of diarylethene crystals on irradiation wavelength of ultraviolet light.

    PubMed

    Kitagawa, Daichi; Tanaka, Rika; Kobatake, Seiya

    2015-11-07

    The dependence of the photoinduced bending behavior of diarylethene crystals on the ultraviolet light irradiation wavelength was investigated. When irradiated with 365 nm light, a crystal of 1,2-bis(5-methyl-2-phenyl-4-thiazolyl)perfluorocyclopentene (1a) bends toward the incident light. On the other hand, when irradiated with 380 nm light, the crystal of 1a first bends away from the light source and then bends toward the incident light. To explain this bending behavior, we propose a comprehensive mechanism based on the depth of the photochromic reaction from the crystal surface. This mechanism is successfully supported by the change of cell parameters associated with the photochromic reaction upon irradiation with 380 nm light, which was determined by in situ X-ray crystallographic analysis.

  18. Protein secondary-shell interactions enhance the photoinduced hydrogen production of cobalt protoporphyrin IX.

    PubMed

    Sommer, Dayn Joseph; Vaughn, Michael David; Ghirlanda, Giovanna

    2014-12-28

    Hydrogen is an attractive fuel with potential for production scalability, provided that inexpensive, efficient molecular catalysts utilizing base metals can be developed for hydrogen production. Here we show for the first time that cobalt myoglobin (CoMyo) catalyzes hydrogen production in mild aerobic conditions with turnover number of 520 over 8 hours. Compared to free Co-protoporphyrin IX, incorporation into the myoglobin scaffold results in a 4-fold increase in photoinduced hydrogen production activity. Engineered variants in which specific histidine resides in proximity of the active site were mutated to alanine result in modulation of the catalytic activity, with the H64A/H97A mutant displaying activity 2.5-fold higher than wild type. Our results demonstrate that protein scaffolds can augment and modulate the intrinsic catalytic activity of molecular hydrogen production catalysts.

  19. Photo-induced current transient spectroscopy of single crystal Tl6I4Se

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Peters, J. A.; Sebastian, M.; Kanatzidis, M. G.; Im, J.; Freeman, A. J.; Wessels, B. W.

    2014-11-01

    The compound Tl6I4Se is a promising wide band gap semiconductor for hard radiation detection at room temperature. To further improve its detection efficiency, native defects have been investigated using photo-induced current transient spectroscopy (PICTS). We observe two shallow acceptor levels with mean activation energies of 76, 175 meV, and two shallow donor defects 62, and 96 meV, respectively. No deeper donor levels are observed. The levels are attributed to native point defects. Defect capture cross sections in the range 10-21 to 10-18 cm2 were measured. The small capture cross sections are attributed to the effective screening of the defects due to a large static dielectric constant.

  20. Direct and real time probe of photoinduced structure transition in colossal magnetoresistive material

    DOE PAGES

    Li, Junjie; Wang, Xuan; Zhou, Haidong; ...

    2016-07-29

    Here, we report a direct and real time measurement of photoinduced structure phase transition in single crystal La0.84Sr0.16MnO3 using femtosecond electron diffraction. The melting of orthorhombic lattice ordering under femtosecond optical excitation is found involving two distinct processes with different time scales, an initial fast melting of orthorhombic phase in about 4 ps and a subsequent slower transformation in 90 ps and longer timescales. Furthermore, the fast process is designated as the initial melting of orthorhombic phase induced by the Mn-O bond change that is most likely driven by the quenching of the dynamic Jahn-Teller distortion following the photo-excitation. Wemore » attribute the slow process to the growing of newly formed structure domain from the photo-excited sites to the neighboring non-excited orthorhombic sites.« less

  1. Photoinduced DNA damage and cytotoxicity by a triphenylamine-modified platinum-diimine complex.

    PubMed

    Zhang, Zhigang; Dai, Ruihui; Ma, Jiajia; Wang, Shuying; Wei, Xuehong; Wang, Hongfei

    2015-02-01

    Many planar photosensitizers tend to self-aggregate via van der Waals interactions between π-conjugated systems. The self-aggregation of the photosensitizer may reduce the efficiency of the photosensitizer to generate singlet oxygen, thereby diminishing its photodynamic activity. Efforts have been made to improve the photodynamic activity of bis-(o-diiminobenzosemiquinonato)platinum(II) which has planar geometry by the introduction of the sterically hindered triphenylamine moiety into the ligand. Herein we report the photoinduced DNA damage and cytotoxicity by a triphenylamine-modified platinum-diimine complex in red light studied by fluorescence spectra, agarose gel assay and cell viability assay. The results suggest that the triphenylamine-modified platinum-diimine complex has better capability to generate singlet oxygen than bis-(o-diiminobenzosemiquinonato)platinum(II), and it can induce DNA damage in red light, causing high photocytotoxicity in HepG-2 cells in vitro.

  2. Surface modification of ultra high molecular weight polyethylene fibers via the sequential photoinduced graft polymerization

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Zhang, Wei; Wang, Xinwei; Mai, Yongyi; Zhang, Yumei

    2011-06-01

    In this study, a sequential photoinduced graft polymerization process was proposed to improve the poor interfacial bonding property of ultra high molecular weight polyethylene (UHMWPE) fibers. The polymerization was initiated by dormant semipinacol (SP) groups and carried out in a thin liquid layer. Methacrylic acid (MAA) and acryl amide (AM) were grafted stepwise onto the surface of UHMWPE fibers. Attenuated total reflectance infrared spectroscopy (ATR-IR) and thermo gravimetric analysis (TGA) confirmed the grafting. The analysis result of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicated the structure of grafted chains. Scanning electron microscopy (SEM) images and atomic force microscopy (AFM) images revealed the apparent morphology changing, and the grafted layers were observed. Interfacial shear stress (IFSS) test of the modified fibers showed an extensively improved interfacial bonding property. The active groups grafted onto the fibers would supply enough anchor points for the chemical bonding with various resins or further reactions.

  3. Photoinduced formation of peroxyl radicals in aqueous solutions of nucleobase derivatives at 77 K

    NASA Astrophysics Data System (ADS)

    Lozinova, T. A.; Lander, A. V.

    2015-05-01

    It is shown that the formation of free radicals photoinduced by near-UV irradiation at 77 K in aqueous solutions of guanosine-5'-monophosphate (GMP), adenosine (Ado), adenine (A), and thymine (T) containing NaCl (0.1 M) is intensified in the presence of O2. Signals of peroxyl radicals O{2/-·} and HO{2/·} are indicated in analyzing EPR spectra, and their overall yield is 20-40% of the total amount of the formed paramagnetic products. It is found that the concentration ratio of O{2/-·} and HO{2/·} radicals depends not only on pH of the solutions before freezing but also on the duration of irradiation and method of freezing the samples. Plausible mechanisms of the processes are discussed.

  4. Photoinduced field-assisted electron emission from dielectric-coated electrodes into gases

    NASA Astrophysics Data System (ADS)

    Josepson, R.; Laan, M.; Aarik, J.; Kasikov, A.

    2008-07-01

    A photoinduced non-self-sustained discharge in a point-plane gap at near-atmospheric pressures in nitrogen and nitrogen-oxygen mixture was studied. Molybdenum and platinum points were coated with thin layers of MgO and TiO2 of different thicknesses. Static current-voltage characteristics were recorded at different intensities of triggering light, layer thickness and gas pressure. The common regularities of current-voltage characteristics were independent of the electrode/coating combinations used. The studies showed that the field-assisted two-step model of emission describes the experimental findings. The electron emission is controlled by Schottky and Fowler-Nordheim mechanisms at the metal-dielectric interface and by a recombination of positive ions with 'hot' and free electrons near the dielectric-gas interface.

  5. Direct and real time probe of photoinduced structure transition in colossal magnetoresistive material

    NASA Astrophysics Data System (ADS)

    Li, Junjie; Wang, Xuan; Zhou, Haidong; Zhou, Jun; Cheng, J. G.; Cao, Jianming

    2016-07-01

    We report a direct and real time measurement of photoinduced structure phase transition in single crystal La0.84Sr0.16MnO3 using femtosecond electron diffraction. The melting of orthorhombic lattice ordering under femtosecond optical excitation is found involving two distinct processes with different time scales, an initial fast melting of orthorhombic phase in about 4 ps and a subsequent slower transformation in 90 ps and longer timescales. The fast process is designated as the initial melting of orthorhombic phase induced by the Mn-O bond change that is most likely driven by the quenching of the dynamic Jahn-Teller distortion following the photo-excitation. The slow process is attributed to the growing of newly formed structure domain from the photo-excited sites to the neighboring non-excited orthorhombic sites.

  6. Photo-induced persistent inversion of germanium in a 200-nm-deep surface region.

    PubMed

    Prokscha, T; Chow, K H; Stilp, E; Suter, A; Luetkens, H; Morenzoni, E; Nieuwenhuys, G J; Salman, Z; Scheuermann, R

    2013-01-01

    The controlled manipulation of the charge carrier concentration in nanometer thin layers is the basis of current semiconductor technology and of fundamental importance for device applications. Here we show that it is possible to induce a persistent inversion from n- to p-type in a 200-nm-thick surface layer of a germanium wafer by illumination with white and blue light. We induce the inversion with a half-life of ~12 hours at a temperature of 220 K which disappears above 280 K. The photo-induced inversion is absent for a sample with a 20-nm-thick gold capping layer providing a Schottky barrier at the interface. This indicates that charge accumulation at the surface is essential to explain the observed inversion. The contactless change of carrier concentration is potentially interesting for device applications in opto-electronics where the gate electrode and gate oxide could be replaced by the semiconductor surface.

  7. Photoinduced Formation of Colloidal Silver in Nitrocellulose Solutions Containing Titanium Alkoxides

    NASA Astrophysics Data System (ADS)

    Kulak, A. I.; Branitsky, G. A.

    2016-07-01

    The study shows the possibility of photo-induced reduction of silver nitrate and formation of stable colloidal silver particles in an isopropanol-N,N-dimethylacetamide solution of titanium alkoxide (polybutyl titanate) stabilized by nitrocellulose. It is established that titanium alkoxide and the products of its partial hydrolysis in the liquid composition play the role of a photocatalyst for the reduction of silver ions; the introduction of nitric or acetic acid additives to the composition significantly increases its photosensitivity. The films deposited from the liquid composition, previously irradiated with visible or UV light, consist of hydrated titanium dioxide and nitrocellulose with incorporated colloidal silver. Thermal treatment of the films at 150-245°C leads to the decomposition of nitrocellulose and an increase in the absorption by silver particles.

  8. Photoinduced fluorescence enhancement in CdSe /ZnS quantum dot monolayers: Influence of substrate

    NASA Astrophysics Data System (ADS)

    Uematsu, Takafumi; Maenosono, Shinya; Yamaguchi, Yukio

    2006-07-01

    Photoinduced fluorescence enhancement (PFE) of CdSe /ZnS core/shell quantum dot (QD) films on SiOx substrates was investigated. The fluorescence intensity of the QD film on SiO1.9 was greatly enhanced by continuous irradiation in vacuum, while the same QD film on SiO0.6 showed a small enhancement of the fluorescence intensity. After irradiation, the rate of fluorescence decay of the QD film on SiO0.6 was smaller than that of the QD film on SiO1.9. Our results suggest that the origin of PFE derives from the photoejection of electrons into the substrate, and that the oxygen-excess-related defects work as trap sites for the electrons.

  9. Control of photoinduced fluorescence enhancement of colloidal quantum dots using metal oxides

    NASA Astrophysics Data System (ADS)

    Sadeghi, Seyed M.; Wing, Waylin J.; Patty, Kira; Campbell, Quinn

    2015-10-01

    It is well known that irradiation of colloidal quantum dots can dramatically enhance their emission efficiencies, leading to so-called photoinduced fluorescence enhancement (PFE). This process is the result of the photochemical and photophysical properties of quantum dots and the way they interact with the environment in the presence of light. It has been shown that such properties can be changed significantly using metal oxides. Using spectroscopic techniques, in this paper we investigate emission of different types of quantum dots (with and without shell) in the presence of metal oxides with opposing effects. We observed significant increase of PFE when quantum dots are deposited on about one nanometer of aluminum oxide, suggesting such oxide can profoundly increase quantum yield of such quantum dots. On the other hand, copper oxide can lead to significant suppression of emission of quantum dots, making them nearly completely dark instantly.

  10. Evidence for Photoinduced Insulator-to-Metal transition in B-phase vanadium dioxide

    PubMed Central

    Lourembam, James; Srivastava, Amar; La-o-vorakiat, Chan; Cheng, Liang; Venkatesan, T.; Chia, Elbert E. M.

    2016-01-01

    Ultrafast optical studies have been performed on epitaxial films of the novel B-phase of vanadium dioxide using temperature-dependent optical pump-probe technique. Signature of temperature-driven metal-to-insulator transition was distinctly observed in the ultrafast dynamics — the insulating phase showed two characteristic electronic relaxation times while the metallic phase showed only one. Beyond a threshold value of the pump fluence, the insulating state collapses into a ‘metallic-like’ phase which can be further subdivided into two regimes according to the lengths of the fast characteristic time. The first regime can be explained by lattice heating due to the optical pump; the other cannot be accounted by simple lattice heating effects alone, and thus offers evidence for a true photoinduced phase transition. PMID:27157532

  11. Inter-Fullerene Electronic Coupling Controls the Efficiency of Photoinduced Charge Generation in Organic Bulk Heterojunctions

    SciTech Connect

    Larson, Bryon W.; Reid, Obadiah G.; Coffey, David C.; Avdoshenko, Stanislav M.; Popov, Alexey A.; Boltalina, Olga V.; Strauss, Steven H.; Kopidakis, Nikos; Rumbles, Garry

    2016-09-26

    Photoinduced charge generation (PCG) dynamics are notoriously difficult to correlate with specific molecular properties in device relevant polymer:fullerene organic photovoltaic blend films due to the highly complex nature of the solid state blend morphology. Here, this study uses six judiciously selected trifluoromethylfullerenes blended with the prototypical polymer poly(3-hexylthiophene) and measure the PCG dynamics in 50 fs-500 ns time scales with time-resolved microwave conductivity and femtosecond transient absorption spectroscopy. The isomeric purity and thorough chemical characterization of the fullerenes used in this study allow for a detailed correlation between molecular properties, driving force, local intermolecular electronic coupling and, ultimately, the efficiency of PCG yield. The findings show that the molecular design of the fullerene not only determines inter-fullerene electronic coupling, but also influences the decay dynamics of free holes in the donor phase even when the polymer microstructure remains unchanged.

  12. Direct and real time probe of photoinduced structure transition in colossal magnetoresistive material

    SciTech Connect

    Li, Junjie; Wang, Xuan; Zhou, Haidong; Zhou, Jun; Cheng, J. G.; Cao, Jianming

    2016-07-29

    Here, we report a direct and real time measurement of photoinduced structure phase transition in single crystal La0.84Sr0.16MnO3 using femtosecond electron diffraction. The melting of orthorhombic lattice ordering under femtosecond optical excitation is found involving two distinct processes with different time scales, an initial fast melting of orthorhombic phase in about 4 ps and a subsequent slower transformation in 90 ps and longer timescales. Furthermore, the fast process is designated as the initial melting of orthorhombic phase induced by the Mn-O bond change that is most likely driven by the quenching of the dynamic Jahn-Teller distortion following the photo-excitation. We attribute the slow process to the growing of newly formed structure domain from the photo-excited sites to the neighboring non-excited orthorhombic sites.

  13. Direct visualization of photoinduced glassy dynamics on the amorphous silicon carbide surface by STM movies

    NASA Astrophysics Data System (ADS)

    Nguyen, Duc; Nienhaus, Lea; Haasch, Richard T.; Lyding, Joseph; Gruebele, Martin

    2015-03-01

    Glassy dynamics can be controlled by light irradiation. Sub- and above-bandgap irradiation cause numerous phenomena in glasses including photorelaxation, photoexpansion, photodarkening and pohtoinduced fluidity. We used scanning tunneling microscopy to study surface glassy dynamics of amorphous silicon carbide irradiated with above- bandgap 532 nm light. Surface clusters of ~ 4-5 glass forming unit in diameter hop mostly in a two-state fashion, both without and with irradiation. Upon irradiation, the average surface hopping activity increases by a factor of 3. A very long (~1 day) movie of individual clusters with varying laser power density provides direct evidence for photoinduced enhanced hopping on the glass surfaces. We propose two mechanisms: heating and electronic for the photoenhanced surface dynamics.

  14. Photoinduced reduction of divalent mercury by quinones in the presence of formic acid under anaerobic conditions.

    PubMed

    Berkovic, Andrea M; Bertolotti, Sonia G; Villata, Laura S; Gonzalez, Mónica C; Pis Diez, Reinaldo; Mártire, Daniel O

    2012-11-01

    The laser flash photolysis technique (λ(exc)=355 nm) was used to investigate the mechanism of the HgCl(2) reduction mediated by CO(2)(-) radicals generated from quenching of the triplet states of 1,4-naphthoquinone (NQ) by formic acid. Kinetic simulations of the experimental signals support the proposed reaction mechanism. This system is of potential interest in the development of UV-A photoinduced photolytic procedures for the treatment of Hg(II) contaminated waters. The successful replacement of NQ with a commercial fulvic acid, as a model compound of dissolved organic matter, showed that the method is applicable to organic matter-containing waters without the addition of quinones.

  15. Dynamics of photoinduced processes in liquid-crystal polymer films containing azo compounds

    SciTech Connect

    Simonov, A N; Larichev, A V

    1999-07-31

    The photoinduced processes in azo-compound-containing side-chain polymer films with liquid-crystal properties are examined theoretically. A model is proposed whereby it is possible to consider the dynamics of the optical response of a medium taking into account the anisotropic saturation in the angular distribution of the azo-dye isomers as well as the intermolecular interaction. The influence of the liquid-crystal ordering in the polymer is taken into account by introducing a phenomenological mean-field factor. Analytical solutions describing changes in the optical properties of a polymer film during the initial illumination stages are in good agreement with experimental data. (this issue is dedicated to the memory of s a akhmanov)

  16. Configuration-Dependent Photoinduced Electron Transfer in Diastereomeric Naphthalene-Amino-Naphthalene Triads.

    PubMed

    Nuin, Edurne; Sastre, German; Pischel, Uwe; Andreu, Inmaculada; Miranda, Miguel A

    2015-09-07

    Novel diastereomeric triads containing two naphthalene chromophores have been designed in which an electron-donating amine moiety is covalently integrated into the connecting bridge. Photophysical studies (steady-state and time-resolved fluorescence) in solvents of different polarity have been performed. A remarkable stereodifferentiation in the intramolecular fluorescence quenching was found in acetonitrile. Laser flash photolysis gave rise to naphthalene-derived radical cations, which were also quenched by the amine with an even higher degree of stereodifferentiation. The results are in agreement with thermodynamic estimations and indicate that photoinduced electron transfer (PET) is the main quenching pathway. Furthermore, theoretical calculations have allowed us to explain the experimentally observed stereodifferentiation in PET quenching.

  17. Effect of temperature, energy gap, and distortion of potential surfaces on photoinduced intramolecular electron transfer

    SciTech Connect

    Islampour, R.; Alden, R.G.; Wu, G.Y.C.; Lin, S.H. )

    1993-07-01

    We report the quantitative examination of the effect of distortion of potential energy surfaces and the temperature effect on photoinduced intramolecular electron transfer (PIET) as a function of electronic energy gap. The results demonstrate the importance of distorted oscillators in determining the dependence of the rate of PIET on the energy gap. This phenomenon may in some cases lead to misinterpretations of experimental data, when undistorted oscillators are assumed to be involved in the PIET process. The condition for observing the linear (rather than parabolic) dependence of the ET rate will be determined using the multimode model. The inclusion of multivibrational modes in the nuclear factors results in energy gap behavior, which is markedly different from the single mode case. Finally, a comparison between PIET and internal conversion is discussed. 25 refs., 5 figs., 3 tabs.

  18. Photo-induced potential barrier in As-Se-Ge films

    NASA Astrophysics Data System (ADS)

    Katyal, S. C.; Okano, S.; Suzuki, M.; Bando, T.

    1988-05-01

    Photo-excited effects in AsSeGe and AsSeGeSn amorphous films have been studied under illumination of different light sources. AsSeGe system exhibited rectifying characteristics under illumination of the light with hν > E g, while AsSeGeSn film did not show such phenomena. The illumination of the IR light along with the light of hν > E g weakened the rectification behavior. The photovoltage and I-V characteristics results suggest the existence of "photo-induced" potential barrier in AsSeGe system, which is considered to concern the creation and destruction of neutral defect states D°.

  19. An Explanation of the Photoinduced Giant Dielectric Constant of Lead Halide Perovskite Solar Cells.

    PubMed

    Almond, Darryl P; Bowen, Chris R

    2015-05-07

    A photoinduced giant dielectric constant of ~10(6) has been found in impedance spectroscopy measurements of lead halide perovskite solar cells. We report similar effects in measurements of a porous lead zirconate titanate (PZT) sample saturated with water. The principal effect of the illumination of the solar cell and of the introduction of water into the pore volume of the PZT sample is a significant increase in conductivity and dielectric loss. This is shown to exhibit low frequency power law dispersion. Application of the Kramers-Kronig relationships show the large measured values of permittivity to be related to the power law changes in conductivity and dielectric loss. The power law dispersions in the electrical responses are consistent with an electrical network model of microstructure. It is concluded that the high apparent values of permittivity are features of the microstructural networks and not fundamental effects in the two perovskite materials.

  20. Enhancing Photoinduced Electron Transfer Efficiency of Fluorescent pH-Probes with Halogenated Phenols

    PubMed Central

    2014-01-01

    Photoinduced electron transfer (PET), which causes pH-dependent quenching of fluorescent dyes, is more effectively introduced by phenolic groups than by amino groups which have been much more commonly used so far. That is demonstrated by fluorescence measurements involving several classes of fluorophores. Electrochemical measurements show that PET in several amino-modified dyes is thermodynamically favorable, even though it was not experimentally found, underlining the importance of kinetic aspects to the process. Consequently, the attachment of phenolic groups allows for fast and simple preparation of a wide selection of fluorescent pH-probes with tailor-made spectral properties, sensitive ranges, and individual advantages, so that a large number of applications can be realized. Fluorophores carrying phenolic groups may also be used for sensing analytes other than pH or molecular switching and signaling. PMID:25126834

  1. The Globular State of the Single-Stranded RNA: Effect of the Secondary Structure Rearrangements

    PubMed Central

    Grigoryan, Zareh A.; Karapetian, Armen T.

    2015-01-01

    The mutual influence of the slow rearrangements of secondary structure and fast collapse of the long single-stranded RNA (ssRNA) in approximation of coarse-grained model is studied with analytic calculations. It is assumed that the characteristic time of the secondary structure rearrangement is much longer than that for the formation of the tertiary structure. A nonequilibrium phase transition of the 2nd order has been observed. PMID:26345143

  2. Wagner–Meerwein-Type Rearrangements of Germapolysilanes - A Stable Ion Study

    PubMed Central

    2015-01-01

    The rearrangement of tris(trimethylsilyl)silyltrimethylgermane 1 to give tetrakis(trimethylsilyl)germane 2 was investigated as a typical example for Lewis acid catalyzed Wagner–Meerwein-type rearrangements of polysilanes and polygermasilanes. Direct 29Si NMR spectroscopic evidence is provided for several cationic intermediates during the reaction. The identity of these species was verified by independent synthesis and NMR characterization, and their transformation was followed by NMR spectroscopy. PMID:26294805

  3. Complex chromosomal rearrangements by single catastrophic pathogenesis in NUT midline carcinoma

    PubMed Central

    Lee, J.-K.; Louzada, S.; An, Y.; Kim, S. Y.; Kim, S.; Youk, J.; Park, S.; Koo, S. H.; Keam, B.; Jeon, Y. K.; Ku, J.-L.; Yang, F.; Kim, T. M.

    2017-01-01

    Background Nuclear protein in testis (NUT) midline carcinoma (NMC) is a rare aggressive malignancy often occurring in the tissues of midline anatomical structures. Except for the pathognomonic BRD3/4–NUT rearrangement, the comprehensive landscape of genomic alterations in NMCs has been unexplored. Patients and methods We investigated three NMC cases, including two newly diagnosed NMC patients in Seoul National University Hospital, and a previously reported cell line (Ty-82). Whole-genome and transcriptome sequencing were carried out for these cases, and findings were validated by multiplex fluorescence in situ hybridization and using individual fluorescence probes. Results Here, we present the first integrative analysis of whole-genome sequencing, transcriptome sequencing and cytogenetic characterization of NUT midline carcinomas. By whole-genome sequencing, we identified a remarkably similar pattern of highly complex genomic rearrangements (previously denominated as chromoplexy) involving the BRD3/4–NUT oncogenic rearrangements in two newly diagnosed NMC cases. Transcriptome sequencing revealed that these complex rearrangements were transcribed as very simple BRD3/4–NUT fusion transcripts. In Ty-82 cells, we also identified a complex genomic rearrangement involving the BRD4–NUT rearrangement underlying the simple t(15;19) karyotype. Careful inspections of rearrangement breakpoints indicated that these rearrangements were likely attributable to single catastrophic events. Although the NMC genomes had >3000 somatic point mutations, canonical oncogenes or tumor suppressor genes were rarely affected, indicating that they were largely passenger events. Mutational signature analysis showed predominant molecular clock-like signatures in all three cases (accounting for 54%−75% of all base substitutions), suggesting that NMCs may arise from actively proliferating normal cells. Conclusion Taken together, our findings suggest that a single catastrophic event in

  4. Thermal rearrangements in 1,2-poly/1,4-hexadiene/s

    NASA Technical Reports Server (NTRS)

    Golub, M. A.

    1978-01-01

    The work described was carried out to study the thermal rearrangements of two unsaturated diene polymers - 1,2-poly(cis-1,4-hexadiene) (CHD) and 1,2-poly(trans-1.4-hexadiene) (THD). It is shown that both CHD and THD have a predominatly 1,8 diene structure and seem to cyclize mainly by the (2 + 2) thermal cycloaddition of double bonds, and to a small extent also by sigmatropic rearrangement with hydrogen shift.

  5. Photo-induced toxicity of titanium dioxide nanoparticles to Daphnia magna under natural sunlight.

    PubMed

    Mansfield, C M; Alloy, M M; Hamilton, J; Verbeck, G F; Newton, K; Klaine, S J; Roberts, A P

    2015-02-01

    Titanium dioxide nanoparticles (TiO2 NP) are one of the most abundantly utilized nanoparticles in the world. Studies have demonstrated the ability of the anatase crystal of TiO2 NP to produce reactive oxygen species (ROS) in the presence of ultraviolet radiation (UVR), a co-exposure likely to occur in aquatic ecosystems. The goal of this study was to examine the photo-induced toxicity of anatase TiO2 NP under natural sunlight to Daphnia magna. D. magna were exposed to a range of UVR intensities and anatase TiO2 concentrations in an outdoor exposure system using the sun as the source of UVR. Different UVR intensities were achieved using UVR opaque and transparent plastics. AnataseTiO2-NP demonstrated the reciprocal relationship seen in other phototoxic compounds such as polycyclic aromatic hydrocarbons (PAHs) at higher UVR treatments. The calculated 8h LC50 of anatase TiO2 NP was 139 ppb under full intensity ambient natural sunlight, 778 ppb under 50% natural sunlight, and >500 ppm under 10% natural sunlight. Mortality was also compared between animals allowed to accumulate a body burden of anatase TiO2 for 1h and organisms whose first exposure to anatase TiO2 aqueous suspensions occurred under UVR. A significantly greater toxic effect was observed in aqueous, low body burden suspensions than that of TiO2 1h body burdens, which is dissimilar from the model presented in PAHs. Anatase TiO2 presents a unique photo-induced toxic model that is different than that of established phototoxic compounds.

  6. Photoinduced Dynamics and Toxicity of a Cancer Drug in Proximity of Inorganic Nanoparticles under Visible Light.

    PubMed

    Chaudhuri, Siddhi; Sardar, Samim; Bagchi, Damayanti; Dutta, Shreyasi; Debnath, Sushanta; Saha, Partha; Lemmens, Peter; Pal, Samir Kumar

    2016-01-18

    Drug sensitization with various inorganic nanoparticles (NPs) has proved to be a promising and an emergent concept in the field of nanomedicine. Rose bengal (RB), a notable photosensitizer, triggers the formation of reactive oxygen species under green-light irradiation, and consequently, it induces cytotoxicity and cell death. In the present study, the effect of photoinduced dynamics of RB upon complexation with semiconductor zinc oxide NPs is explored. To accomplish this, we successfully synthesized nanohybrids of RB with ZnO NPs with a particle size of 24 nm and optically characterized them. The uniform size and integrity of the particles were confirmed by high-resolution transmission electron microscopy. UV/Vis absorption and steady-state fluorescence studies reveal the formation of the nanohybrids. ultrafast picosecond-resolved fluorescence studies of RB-ZnO nanohybrids demonstrate an efficient electron transfer from the photoexcited drug to the semiconductor NPs. Picosecond-resolved Förster resonance energy transfer from ZnO NPs to RB unravel the proximity of the drug to the semiconductor at the molecular level. The photoinduced ROS formation was monitored using a dichlorofluorescin oxidation assay, which is a conventional oxidative stress indicator. It is observed that the ROS generation under green light illumination is greater at low concentrations of RB-ZnO nanohybrids compared with free RB. Substantial photodynamic activity of the nanohybrids in bacterial and fungal cell lines validated the in vitro toxicity results. Furthermore, the cytotoxic effect of the nanohybrids in HeLa cells, which was monitored by MTT assay, is also noteworthy.

  7. Optimizing organic photovoltaics using tailored heterojunctions: A photoinduced absorption study of oligothiophenes with low band gaps

    NASA Astrophysics Data System (ADS)

    Schueppel, R.; Schmidt, K.; Uhrich, C.; Schulze, K.; Wynands, D.; Brédas, J. L.; Brier, E.; Reinold, E.; Bu, H.-B.; Baeuerle, P.; Maennig, B.; Pfeiffer, M.; Leo, K.

    2008-02-01

    A power conversion efficiency of 3.4% with an open-circuit voltage of 1V was recently demonstrated in a thin film solar cell utilizing fullerene C60 as acceptor and a new acceptor-substituted oligothiophene with an optical gap of 1.77eV as donor [K. Schulze , Adv. Mater. (Weinheim, Ger.) 18, 2872 (2006)]. This prompted us to systematically study the energy- and electron transfer processes at the oligothiophene:fullerene heterojunction for a homologous series of these oligothiophenes. Cyclic voltammetry and ultraviolet photoelectron spectroscopy data show that the heterojunction is modified due to tuning of the highest occupied molecular orbital energy for different oligothiophene chain lengths, while the lowest unoccupied molecular orbital energy remains essentially fixed due to the presence of electron-withdrawing end groups (dicyanovinyl) attached to the oligothiophene. Use of photoinduced absorption (PA) allows the study of the electron transfer process at the heterojunction to C60 . Quantum-chemical calculations performed at the density functional theory and/or time-dependent density functional theory level and cation absorption spectra of diluted DCVnT provide an unambiguous identification of the transitions observed in the PA spectra. Upon increasing the effective energy gap of the donor-acceptor pair by increasing the ionization energy of the donor, photoinduced electron transfer is eventually replaced with energy transfer, which alters the photovoltaic operation conditions. The optimum open-circuit voltage of a solar cell is thus a trade-off between efficient charge separation at the interface and maximized effective gap. It appears that the open-circuit voltages of 1.0-1.1V in our solar cell devices have reached an optimum since higher voltages result in a loss in charge separation efficiency.

  8. Photo-induced electronic properties in single quantum well system: effect of excitonic lifetime

    NASA Astrophysics Data System (ADS)

    Patwari, Jayita; Ghadi, Hemant; Sardar, Samim; Singhal, Jashan; Tongbram, Binita; Shyamal, Sanjib; Bhattacharya, Chinmoy; Chakrabarti, Subhananda; Pal, Samir Kumar

    2017-01-01

    In the present study, we have established a correlation between the photo-induced electronic phenomena and excited state lifetime of the photo generated carriers in double barrier Al0.3Ga0.7As\\GaAs quantum well (QW) structures. The excited state lifetime was measured experimentally by picosecond time resolved photoluminescence spectroscopy for two samples with different well widths (5.3 nm and 16.5 nm). The faster nonradiative decay time of the narrower well can be attributed to the facile escape of electrons from well to barrier due to lower associated energy compared to that of the thicker well which resembles the simulated results of the energy level distribution. The proposed mechanism of carrier escape is further proven from the higher value of unconventional excitonic capacitance value in the thicker well, measured by impedance spectroscopy. The dependence of photo-induced capacitance on well thickness is explained by the lifetime of the excited carriers in this study. Dependence of the photo-generated capacitance (C) on externally applied bias voltage (V) was also studied to quantitatively establish a proportional relation between the carrier holding capacity of the well and the excitonic lifetime. The higher accumulation of charge and lower ground state energy of the thicker well is evident from the higher tunnelling current found for the same in the photocurrent (I) versus voltage (V) measurement. Thus the escape of electrons from the well to barrier is the key factor affecting the photo generated charge accumulation and its holding capacity which in turn influences the device performances.

  9. Ab initio spectroscopy and photoinduced cooling of the trans-stilbene molecule.

    PubMed

    Tatchen, Jörg; Pollak, Eli

    2008-04-28

    We present a theoretical study of the S(0)-->S(1) and S(0)<--S(1) vibronic spectra for trans-stilbene. Franck-Condon spectra in the harmonic approximation are generated for the complete system with 72 degrees of freedom by means of an analytic time-dependent approach accounting for Dushinsky rotations and thermal effects. The force fields are computed by means of density functional theory (DFT) and time-dependent DFT, on the one hand, and ab initio complete active space self-consistent field theory, on the other hand. The B3LYP functional shows that almost planar potential energy surface minima are found for the S(0) and S(1) state. Imposing C(2h) symmetry constraints, we obtain low-temperature high-resolution Franck-Condon spectra for both absorption and emission which are in reasonably good agreement with the experimental spectra measured by Syage et al. [J. Chem. Phys. 81, 4685 (1984)] in supersonic jets. Due to thermal population of low-energy modes, the room temperature absorption spectrum is very broad. An almost structureless band which extends over several thousand cm(-1) is obtained from the present theory and agrees with the experimental absorption band shape. Finally, within the harmonic model, we study the effect of photoexcitation on the energy distribution in the excited S(1) state. We find noticeable cooling of approximately 20 K within a frequency interval spanning from -400 to 200 cm(-1) around the 0-0 transition. This indicates that photoinduced cooling must be taken into account when considering the dynamics of the photoinduced isomerization of trans-stilbene. Moreover, this is not the final word, as anharmonicity of the low frequency modes must be taken into account to obtain a full picture which would explain both the energy dependence of the isomerization rates as well as the dependence on the pressure of an external buffer gas.

  10. Photoinduced electron transfer interaction of anthraquinones with aniline quenchers: Influence of methyl substitution in aniline donors

    NASA Astrophysics Data System (ADS)

    Sivakumar, V.; Ponnamma, Deepalekshmi; Hussein, Yasser H. A.

    2017-02-01

    Photoinduced electron transfer between triplet state of 9,10-anthraquinone (AQ) and its two derivatives: 2-chloro-9,10-anthraquinone (CAQ) and sodium anthraquinone-2-sulfonate (AQS) and ground state aniline (AN) and its dimethyl substitutions: 2,3-dimethylaniline (2,3-DMA), 2,6-dimethylaniline (2,6-DMA), 3,5-dimethylaniline (3,5-DMA) and N,N-dimethylaniline (N,N-DMA) is studied using nanosecond laser flash photolysis at room temperature. Detection of radical bands of quinone anions and aniline cations along with their formation and/or decay kinetics are used to confirm the electron transfer (ET) process. In MeCN medium, AN quenches the triplet state of CAQ (CAQT) but not the triplets AQT or AQST. However in aqueous medium, AN quenches AQST and forms radical ion pair. All the DMAs can react through ET with all the triplet quinones at different degrees of efficiency in MeCN medium. Noticeably, the ring substituted DMAs are less efficient in electron donation to AQT or AQST while the N,N-DMA shows high efficiency in donating electron to all triplet quinones in MeCN medium. Charge distribution of donor molecules, in MeCN medium is calculated using density functional theory (DFT), and shows an enhancement of electron density of the ring of N,N-DMA, making it an ideal electron donor for ET studies compared to other DMAs. This systematic selection and usage of anilines with electrochemically tunable quinones can be viewed as a working model of donor-acceptor system that can be utilized in photoinduced ET applications.

  11. Effect of irradiance spectra on the photoinduced toxicity of three polycyclic aromatic hydrocarbons

    SciTech Connect

    Diamond, S.A.; Mount, D.R.; Burkhard, L.P.; Ankley, G.T.; Makynen, E.A.; Leonard, E.N.

    2000-05-01

    Photoinduced toxicity of polycyclic aromatic hydrocarbons (PAHs) is dependent on the concentration of compounds present and the dose of light received. Of the light present, only those wavelengths absorbed by the compound have the potential to initiate the photochemical events underlying phototoxicity. This suggests that variation in light spectra present in natural waters, arising from variation in dissolved organic carbon composition, is an important determinant of phototoxicity risk in specific, PAH-contaminated waterbodies. To quantify the effect of environmentally realistic variation in light spectra on toxicity, brine shrimp (Artemia salina) assays were conducted under various light spectra and with three PAHs (pyrene, fluoranthene, and anthracene) of known phototoxicity potential. In these spectral assays, the total ultraviolet light present was equivalent; only the spectral characteristics varied. Based on the absorbance spectra of these PAHs, it was predicted that toxicity, quantified using immobilization as the endpoint, would vary significantly among light spectra in pyrene assays, but not in anthracene assays, and that variation in toxicity in fluoranthene assays would be intermediate. The results supported these assumptions. In the pyrene exposures, the glass filter time to 50% population immobilization (IT50) (39.5 min) was 117% longer than the KCr filter IT50 (18.2 min). In the fluoranthene exposures, the glass filter IT50 (49.5 min) was 27% longer than the KCr filter IT50 (39.1 min). In the anthracene exposures, the glass filter IT50 (62.2 min) was not statistically different from the KCr filter IT50 (63.8 min). Comparison of these results with the results of assays conducted under neutral-density filters (that change intensity but not spectral distribution) demonstrate that multiplying spectral intensity by wavelength-specific absorbance accurately predicts relative photoinduced toxicity among the experimental treatments. These results indicate

  12. Photoinduced aging and viscosity evolution in Se-rich Ge-Se glasses

    SciTech Connect

    Gueguen, Yann; Sangleboeuf, Jean-Christophe; Rouxel, Tanguy; King, Ellyn A.; Lucas, Pierre; Keryvin, Vincent; Bureau, Bruno

    2013-08-21

    We propose here to investigate the non-equilibrium viscosity of Ge-Se glasses under and after light irradiation. Ge{sub 10}Se{sub 90} and Ge{sub 20}Se{sub 80} fibers have been aged in the dark and under ambient light, over months. During aging, both the relaxation of enthalpy and the viscosity have been investigated. The viscosity was measured by shear relaxation-recovery tests allowing the measurement of non-equilibrium viscosity. When Ge{sub 10}Se{sub 90} glass fibers are aged under irradiation, a relatively fast fictive temperature decrease is observed. Concomitantly, during aging under irradiation, the non-equilibrium viscosity increases and reaches an equilibrium after two months of aging. This viscosity increase is also observed in Ge{sub 20}Se{sub 80} fibers. Nevertheless, this equilibrium viscosity is far below the viscosity expected at the configurational equilibrium. As soon as the irradiation ceases, the viscosity increases almost instantaneously by about one order of magnitude. Then, if the fibers are kept in the dark, their viscosity slowly increases over months. The analysis of the shear relaxation functions shows that the aging is thermorheologically simple. On the other side, there is no simple relaxation between the shear relaxation functions measured under irradiation and those measured in the dark. These results clearly suggest that a very specific photoinduced aging process occurs under irradiation. This aging is due to photorelaxation. Nevertheless, the viscosity changes are not solely correlated to photoaging and photorelaxation. A scenario is proposed to explain all the observed viscosity evolutions under and after irradiation, on the basis of photoinduced transient defects.

  13. Chromosomal rearrangements directly cause underdominant F1 pollen sterility in Mimulus lewisii-Mimulus cardinalis hybrids.

    PubMed

    Stathos, Angela; Fishman, Lila

    2014-11-01

    Chromosomal rearrangements can contribute to the evolution of postzygotic reproductive isolation directly, by disrupting meiosis in F1 hybrids, or indirectly, by suppressing recombination among genic incompatibilities. Because direct effects of rearrangements on fertility imply fitness costs during their spread, understanding the mechanism of F1 hybrid sterility is integral to reconstructing the role(s) of rearrangements in speciation. In hybrids between monkeyflowers Mimulus cardinalis and Mimulus lewisii, rearrangements contain all quantitative trait loci (QTLs) for both premating barriers and pollen sterility, suggesting that they may have facilitated speciation in this model system. We used artificial chromosome doubling and comparative mapping to test whether heterozygous rearrangements directly cause underdominant male sterility in M. lewisii-M. cardinalis hybrids. Consistent with a direct chromosomal basis for hybrid sterility, synthetic tetraploid F1 s showed highly restored fertility (83.4% pollen fertility) relative to diploids F1 s (36.0%). Additional mapping with Mimulus parishii-M. cardinalis and M. parishii-M. lewisii hybrids demonstrated that underdominant male sterility is caused by one M. lewisii specific and one M. cardinalis specific reciprocal translocation, but that inversions had no direct effects on fertility. We discuss the importance of translocations as causes of reproductive isolation, and consider models for how underdominant rearrangements spread and fix despite intrinsic fitness costs.

  14. Rearrangement dynamics in colloidal particle packings identified through local structure and machine-learning

    NASA Astrophysics Data System (ADS)

    Davidson, Zoey S.; Still, Tim; Gratale, Matthew D.; Ma, Xiaoguang; Schoenholz, Samuel S.; Sussman, Daniel M.; Liu, A. J.; Yodh, A. G.

    We explore the connection between measures of local structure and particle rearrangements in soft thermal quasi-two-dimensional colloidal systems employing a machine learning approach. Local structure is characterized by two and three point structure functions that measure radial and angular distributions of particles, and rearrangements are identified by a measure of change in average colloidal particle position. By generating labeled training data, we can extract the features of these functions that contribute to the likelihood of a rearrangement. In particular, we use a machine-learning algorithm to construct a decision function in the form of a scalar field we call softness that with high accuracy labels regions of particles more likely to rearrange. Thus, we can predict dynamic rearrangements from the instantaneous local structure. The softness field remains a good predictor when we vary the packing fraction between training and test data sets. In glassy samples, the softness field can identify aging as particles become less likely to undergo cage rearrangements. We gratefully acknowledge financial support through NSF DMR12-05463, MRSEC DMR11-20901, NASA NNX08AO0G, and DE-FG02-05ER46199.

  15. Delineating Rearrangements in Single Yeast Artificial Chromosomes by Quantitative DNA Fiber Mapping

    SciTech Connect

    Weier, Heinz-Ulrich G.; Greulich-Bode, Karin M.; Wu, Jenny; Duell, Thomas

    2009-09-18

    Cloning of large chunks of human genomic DNA in recombinant systems such as yeast or bacterial artificial chromosomes has greatly facilitated the construction of physical maps, the positional cloning of disease genes or the preparation of patient-specific DNA probes for diagnostic purposes. For this process to work efficiently, the DNA cloning process and subsequent clone propagation need to maintain stable inserts that are neither deleted nor otherwise rearranged. Some regions of the human genome; however, appear to have a higher propensity than others to rearrange in any host system. Thus, techniques to detect and accurately characterize such rearrangements need to be developed. We developed a technique termed 'Quantitative DNA Fiber Mapping (QDFM)' that allows accurate tagging of sequence elements of interest with near kilobase accuracy and optimized it for delineation of rearrangements in recombinant DNA clones. This paper demonstrates the power of this microscopic approach by investigating YAC rearrangements. In our examples, high-resolution physical maps for regions within the immunoglobulin lambda variant gene cluster were constructed for three different YAC clones carrying deletions of 95 kb and more. Rearrangements within YACs could be demonstrated unambiguously by pairwise mapping of cosmids along YAC DNA molecules. When coverage by YAC clones was not available, distances between cosmid clones were estimated by hybridization of cosmids onto DNA fibers prepared from human genomic DNA. In addition, the QDFM technology provides essential information about clone stability facilitating closure of the maps of the human genome as well as those of model organisms.

  16. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Photoinduced anisotropy of the refractive index of an azopolymer with liquid-crystal properties

    NASA Astrophysics Data System (ADS)

    Andreeva, M. S.; Shmalgauzen, V. I.

    2004-01-01

    The formation of a photoinduced refractive-index grating in a photosensitive azopolymer with liquid-crystal (LC) properties is theoretically studied. Equations for photoinduced additions to the refractive index of the LC and amorphous polymers are obtained from balance equations for the distribution densities of trans- and cis-isomers of azodyes. The frequency characteristics of the response of the refractive index to a harmonic perturbation are calculated for different values of the LC order parameter.

  17. Advanced lung adenocarcinomas with ROS1-rearrangement frequently show hepatoid cell

    PubMed Central

    Kong, Mei; Zhou, Jianya; Ding, Wei; Zhou, Jianying

    2016-01-01

    Defining distinctive histologic characteristics of ROS1-rearranged non-small-cell lung carcinomas (NSCLCs) may help identify cases that merit molecular testing. However, the majority of previous reports have focused on surgical specimens but only limited studies assessed histomorphology of advanced NSCLCs. In order to identify the clinical and histological characteristics of ROS1-rearranged advanced NSCLCs, we examined five hundred sixteen Chinese patients with advanced NSCLCs using ROS1 fluorescence in situ hybridization and real-time polymerase chain reaction and then analyzed for clinical and pathological features. We performed univariate and multivariate analyses to identify predictive factors associated with ROS1 rearrangement. 19 tumors were identified with ROS1 rearrangement (3.7% of adenocarcinomas). 16 ROS1+ and 122 ROS1- samples with available medical records and enough tumor cells were included for histological analysis. Compared with ROS1-negative advanced NSCLCs, ROS1-rearranged advanced NSCLCs were associated with a younger age at presentation. ROS1 rearrangements were not significantly associated with sex, smoking history, drinking history and metastatic sites. The most common histological pattern was solid growth (12/16), followed by acinar (4/16) growth. 66.7% cases with solid growth pattern showed hepatoid cytology (8/12) and 75% cases with acinar growth pattern showed a cribriform structure (3/4). 18.8% cases were found to have abundant extracellular mucus or signet-ring cells (3/16). Only one case with solid growth pattern showed psammomatous calcifications. In conclusion, age, hepatoid cytology and cribriform structure are the independent predictors for ROS1-rearranged advanced NSCLCs, recognizing these may be helpful in finding candidates for genomic alterations, especially when available tissue samples are limited. PMID:27708233

  18. Role of polytypism and degree of hexagonality on the photoinduced optical second harmonic generation in SiC nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Semenov, A.; Puziko, V.; Skorik, S.; Wojciechowski, A.; Fedorchuk, A. O.; Maciąg, A.

    2015-05-01

    Photoinduced optiсal second harmonic generation was studied in nanocrystalline SiC films prepared by the method of direct ion deposition. For the studies were chosen three types of polytypes (with different degree of hexagonality) - 24R with degree hexagonality G=25, 27R-G=44, 33R with - G=36. The bicolor photoinduced treatment was performed by the wavelengths 1064nm/532 nm by 15 ns YAG:Nd laser. The efficiency of the output SHG was evaluated by ratio of the corresponding signal intensities with respect to the references and by the time delay between the SHG and the fundamental maxima. Explanation of the observed effect is given within a framework of the occurrence of the nano-trapping levels in the film crystalline interfaces.

  19. Ultrafast in cellulo photoinduced dynamics processes of the paradigm molecular light switch [Ru(bpy)2dppz]2+

    NASA Astrophysics Data System (ADS)

    de La Cadena, Alejandro; Davydova, Dar’Ya; Tolstik, Tatiana; Reichardt, Christian; Shukla, Sapna; Akimov, Denis; Heintzmann, Rainer; Popp, Jürgen; Dietzek, Benjamin

    2016-09-01

    An in cellulo study of the ultrafast excited state processes in the paradigm molecular light switch [Ru(bpy)2dppz]2+ by localized pump-probe spectroscopy is reported for the first time. The localization of [Ru(bpy)2dppz]2+ in HepG2 cells is verified by emission microscopy and the characteristic photoinduced picosecond dynamics of the molecular light switch is observed in cellulo. The observation of the typical phosphorescence stemming from a 3MLCT state suggests that the [Ru(bpy)2dppz]2+ complex intercalates with the DNA in the nucleus. The results presented for this benchmark coordination compound reveal the necessity to study the photoinduced processes in coordination compounds for intracellular use, e.g. as sensors or as photodrugs, in the actual biological target environment in order to derive a detailed molecular mechanistic understanding of the excited-state properties of the systems in the actual biological target environment.

  20. Ultrafast in cellulo photoinduced dynamics processes of the paradigm molecular light switch [Ru(bpy)2dppz]2+

    PubMed Central

    De la Cadena, Alejandro; Davydova, Dar’ya; Tolstik, Tatiana; Reichardt, Christian; Shukla, Sapna; Akimov, Denis; Heintzmann, Rainer; Popp, Jürgen; Dietzek, Benjamin

    2016-01-01

    An in cellulo study of the ultrafast excited state processes in the paradigm molecular light switch [Ru(bpy)2dppz]2+ by localized pump-probe spectroscopy is reported for the first time. The localization of [Ru(bpy)2dppz]2+ in HepG2 cells is verified by emission microscopy and the characteristic photoinduced picosecond dynamics of the molecular light switch is observed in cellulo. The observation of the typical phosphorescence stemming from a 3MLCT state suggests that the [Ru(bpy)2dppz]2+ complex intercalates with the DNA in the nucleus. The results presented for this benchmark coordination compound reveal the necessity to study the photoinduced processes in coordination compounds for intracellular use, e.g. as sensors or as photodrugs, in the actual biological target environment in order to derive a detailed molecular mechanistic understanding of the excited-state properties of the systems in the actual biological target environment. PMID:27644587