Anomalous Band Research Articles

Characterization and Fluorescence of Macrocyclic Polystyrene by Anionic End to End Coupling. Role of Coupling Reagents

Macrocyclic polystyrene (PS) was synthesized by initiation of styrene by naphthalide anion or benzylic dianions in the presence of Li or K ions followed by reaction of the resulting PS dianions with dibromomethane (DBM) or 1,4-bis(bromomethylbenzene) (DBX) in THF at −78 °C under high dilution conditions. MALDI and NMR studies of the DBM cycles showed the presence of 1,2-diphenyl linkages. Fluorescence studies on the DBM cycles show strongly enhanced and anomalous structured emission bands between 300 and 320 nm attributable to linear chains containing styrenic chain end impurities. This indicates rapid metal bromine exchange to give chain end benzyl bromides that eliminate with polystyryl anion to give small (<1.0%) fractions of styrene type chain end structures. In comparison, the cycles obtained with DBX show only the PS monomer and excimer bands at 285 and 330 nm, respectively, and appear to be substantially free of such side reactions. These DBX coupled cycles show up to a 2-fold enhancement in the mo...

Observation of anomalous insertion of the medial meniscus on the anterior cruciate ligament

We wanted to determine the frequency of occurrence and types of anomalous insertions of the medial meniscus to the anterior cruciate ligament (ACL) in Finnish patients. In 987 consecutive arthroscopies from January 1996 to August 1998, the meniscal pathology was mapped using videoprints and drawings. We found 11 anomalous medial meniscus insertions to the ACL. There were 4 female and 6 male patients in the series. In 1 woman, the anomaly was bilateral. The mean age of the patients was 30.6 years (range 14 to 63 years). The anomalous band was excised in all patients. The anomaly usually was not the finding that caused the need for arthroscopy. In 3 knees, the anomaly was the only pathologic finding. The frequency of this anomaly occurring was approximately 1.2%. The anomalous medial meniscus insertion to the ACL is a very rare clinical finding. Arthroscopic surgeons should be aware of its existence as well as of other anterior horn insertion variations of the medial meniscus.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 2 (February), 2002: E9

Tetralogy of Fallot: Total Correction

he events that give rise to the c1evelol)iiieiit of the T constellation of lesions that we refer to as tetralogj of Fallot are still micertain. Regardless of the true teleological cause, it is hel1)ful for the surgeon to approach this defect as resulting from anterocephalad deviation of the ventricular outlet septum. "monology with sequellae." The resulting malalignment ventricular septal defect (VSD), aortic override, ancl right ventricular outflow tract ol~struction are thus easily understood. The right ventricular hypertrophy can he appreciated as secondary to the VSD and right ventricular outflow tract ohstructioii. Right ventricular outflow obstruction is increased by hypertrophy of the anterior limb of the septal ]land, anomalous anterior muscular bands, and outlet septum as well as pulmonary valve and arterial anomalies (Fig I). Classically the VSD is circular, juxtaaortic, and nonrestrictive and results from the malalignment of the parietal extension of the infundibular and trabecular septae. As such, the defect lies between the infundibular septum and is cradled by the anterior and posterior limbs of the septal band (Fig 11).

Infrared reflection–absorption properties of platinum nanoparticle films on metal electrode substrates: control of anomalous optical effects

A simple method is described for preparing ultrathin films of carbon-supported platinum nanoparticles on gold and other substrates for examination by electrochemical infrared reflection–absorption spectroscopy (EC-IRAS) in which the anomalous “anti-absorbance” properties commonly observed for metal particle arrays can be minimized as well as controlled. The tactic involves physical deposition as an aqueous suspension, followed by drying and thorough rinsing. The Pt monolayer-level films prepared by this means exhibit largely positive unipolar absorbance bands for CO adlayers, whereas an anomalous inverted band component appears for thicker films, especially those featuring high Pt nanoparticle loadings. These findings demonstrate the value of the film preparation tactic for exploring the electrocatalytic properties of C/Pt materials by using combined electrochemical and EC-IRAS measurements.

Abnormal behavior in the three-photon resonance enhanced multiphoton ionization spectroscopy of CO E 1Π←X 1Σ+(0,0)

The abnormal behavior of CO E 1Π(v=0)←X 1Σ+(v=0) three-photon resonance enhanced multiphoton ionization (REMPI) spectroscopy is studied, including the anomalous band structures and adverse pressure effects on the spectral intensity. One- and two-color experiments with laser beams in co- and counterpropagations have been performed to elucidate the mechanisms. It is demonstrated that the abnormalities originate from two mechanisms, i.e., the reabsorption of the resultant third harmonic generation (THG) in the one-color case or four wave mixing sum frequency generation (FWSFG) in the two-color case, and the interference cancellation between the one-photon excitation channel induced by THG/FWSFG reabsorption and the three-photon direct excitation channel. The former mechanism dominates in the wing region of a resonant transition profile, while the latter is restricted within the kernel portion of the transition.

Nesting Properties and Anomalous Band Effect in MgB2

First principle FLAPW band calculations of the new superconductor MgB2 were performed and the polarization function P12(Q) between the two p-bands mainly formed of boron pz-orbital was calculated. We found that P12(Q) is substantially enhanced around Q=(0,0,p/c), which supports the two-band mechanism of superconductivity for MgB2. P12(Q) peaks at Qz ~ 0.3(2p/c) and Qz \~ 0.5(2p/c). These two peaks are related to the nesting of these Fermi surfaces, but significantly deviates from the position expected from the simplest tight-binding bands for the p-bands. From the calculations for different lattice parameters, we have found significant dependences on the isotopic species of B and on the pressure effect of the polarization function in accordance with the respective changes of Tc in the above-mentioned framework.

Nesting Properties and Anomalous Band Effect in MgB2

First principle FLAPW band calculations of the new superconductor MgB 2 were performed and the polarization function Π 12 ( Q ) between the two π-bands mainly formed of boron p z -orbital was calculated. We found that Π 12 ( Q ) is substantially enhanced around Q =(0, 0, π/ c ), which supports the two-band mechanism of superconductivity for MgB 2 . Π 12 ( Q ) peaks at Q z ∼0.3(2π/ c ) and Q z ∼0.5(2π/ c ). These two peaks are related to the nesting of these Fermi surfaces, but significantly deviates from the position expected from the simplest tight-binding bands for the π-bands. From the calculations for different lattice parameters, we have found significant dependences on the isotopic species of B and on the pressure effect of the polarization function in accordance with the respective changes of T c in the above-mentioned framework.

The Features of Infrared Absorption of the Protein Molecules in the Living System**The project supported by National Natural Science Foundation of China (Grant No. 19974034)

We utilize a vibron-soliton model for amide-I vibrational quanta interacting with optical phonons to study the feature of infrared absorption of the protein molecules with finite temperature. The self-trapping of amide-I vibrational quantum results in red shift of the main peak and largely anomalous band to occur in the infrared absorption for the protein molecules. Utilizing the concise model of vibron and improved theory of color centers we have given theoretically the value of red shifts of the main peak and the intensity of anomalous band in infrared absorption, respectively, the latter reduces with increasing temperature which is consistent with the experimental result.

Echocardiographic diagnosis of left ventricular density: Diagnostic pitfalls

A 75-YEAR-OLD woman was referred for evaluation 10 days after acute anterior wall myocardial infarction. Cardiac catheterization showed depressed left ventricular ejection fraction (25%) and anteroseptal akinesia. No other abnormalities were seen. Coronary angiography revealed occlusion of the left anterior descending (LAD) coronary artery with small-caliber circumflex and right coronary arteries. Urgent off-pump coronary artery bypass graft surgery to the LAD was scheduled for the next day. After induction of general anesthesia, transesophageal echocardiography (TEE) was performed. A transgastric midpapillary view of the left ventricle showed a moderate size (3 cm × 3 cm) echo-dense mass together with areas of calcification (Fig 1). Differential diagnosis included an intraventricular thrombus, a prominent papillary muscle, or an anomalous band. Moderate dyskinesia of the left ventricular apex was also noted. Left ventricular ejection fraction was estimated to be around 25%. What is the diagnosis?

Low-macroscopic-field electron emission from carbon films and other electrically nanostructured heterogeneous materials: hypotheses about emission mechanism

Thin flat dielectric films can be low-macroscopic-field (LMF) electron emitters, able to generate electrons when subject to a macroscopic electric field in the range 1–50 V μm −1. This phenomenon is a known cause of pre-breakdown currents in high-voltage vacuum breakdown, and is now the basis of a broad-area electron-source technology, using carbon-based thin films and other materials. The phenomenon occurs because the dielectric film is, or becomes, an electrically nanostructured heterogeneous (ENH) material, with quasi-filamentary conducting channels between its surfaces. These channels connect to emitting features near or on the film/vacuum surface, or act as electron emitters themselves. The film may contain conducting or semiconducting particles that assist with conductivity and/or act as emitting features. Several forms of thin-film LMF emitter exist: in each case the situation geometry ensures that sufficient field enhancement occurs at the ‘tip’ of the emitting feature for the emission process to be some form of tunnelling field electron emission (probably ‘cold’ in some cases, ‘hot’ in others). This paper explores aspects of the theory of thin-film LMF emission, starting from the need to understand the behaviour of emitters based on amorphous carbon films. A summary review, with extensive references, is given of relevant past work outside the immediate ‘carbon field emission’ context. Relevant aspects of semiconductor field emission theory are noted. Comment is made on the original experiments on diamond field emission, and on theoretical misconceptions in the carbon field emission literature. Analysis of carbon-film emitter behaviour suggests that emission must primarily be due to geometrical field enhancement, that in at least some cases arises from conducting nanostructure inside the film. In one case, published film characteristics can be used to show that sufficient field enhancement should be available. Some problems with an ‘internal field enhancement’ hypothesis are considered and disposed of. Difficulties with Latham’s theory of field-induced emission from ENH materials are pointed out: a new theory, largely qualitative at this stage, can explain longstanding problems: this assumes that dielectric films must be treated as ‘hopping conductors’ not semiconductors. Electron emission takes place via localised surface states: transition to a channel-limited current regime takes place when the surface states no longer have high enough occupation probability to screen the external field, and is accompanied by anomalous band bending at the channel tip. Mathematical theories of band bending and field emission for hopping conductors are required. Some consequences for the design of LMF emitters are noted.

Excited state photodynamics of 4- N, N-dimethylamino cinnamaldehyde: : A solvent dependent competition of TICT and intermolecular hydrogen bonding

This paper describes the dual fluorescence of 4- N, N-dimethylamino cinnamaldehyde (DMACA) in various solvents. Based on major findings the first fluorescence band has been assigned to be arising out of delocalized excited state (DE) and the anomalous fluorescence band in polar aprotic solvents has been assigned to twisted intramolecular charge transfer (TICT) state whereas, in protic solvent it is arising out due to hydrogen bonding interaction between hydrogen donor part of the solvent and carbonyl group of the probe molecule. This hydrogen bonding being an efficient fluorescence quenching channel trammels the TICT formation and thus an apparent competition exists between TICT and hydrogen bonding formation in protic solvent. The calculated absorption spectrum generated from CNDO calculations follows nicely the experimental absorption band. The AM1 calculations corroborate the large dipole moment change and the charge transfer in orthogonal position as found from experimental observations.

Inhibition of Human Telomerase by 7-Deaza-2′-deoxyguanosine Nucleoside Triphosphate Analogs: Potent Inhibition by 6-Thio-7-deaza-2′-deoxyguanosine 5′-Triphosphate

We have examined analogs of the previously reported 7-deaza-2′-deoxypurine nucleoside triphosphate series of human telomerase inhibitors. Two new telomerase-inhibiting nucleotides are reported: 6-methoxy-7-deaza-2′-deoxyguanosine 5′-triphosphate (OMDG-TP) and 6-thio-7-deaza-2′-deoxyguanosine 5′-triphosphate (TDG-TP). In particular, TDG-TP is a very potent inhibitor of human telomerase with an IC50 of 60 nM. TDG-TP can substitute for dGTP as a substrate for telomerase, but only at relatively high concentrations. Under conditions in which TDG-TP is the only available guanosine substrate, telomerase becomes nonprocessive, synthesizing short products that appear to contain only one to three TDG residues. Similarly, the less potent telomerase inhibitor OMDG-TP gives rise to short telomerase products, but less efficiently than TDG-TP. We show here that TDG-TP, and to a lesser extent OMDG-TP, can serve as substrates for both templated (Klenow exo) and nontemplated (terminal transferase) DNA polymerases. For either polymerase, the products arising from TDG-TP are relatively short, and give rise to bands of unusual mobility under PAGE conditions. These anomalous bands revert, under treatment with DTT, to normal mobility bands, indicating that these products may contain thiol-labile disulfide linkages involving the incorporated TDG residues. This observation of potential TDG-crosslinks may have bearing on the mechanism of telomerase inhibition by this nucleotide analog.

High Pressure Photoluminescence Study of the GaAs/Partially Ordered GaInP Interface

Using time-resolved (TRPL) and continuous-wave photoluminescence (CWPL) we have studied GaAs/partially ordered Ga0.5In0.5P single quantum well samples at pressures up to ≈5 GPa. In such samples emission from the quantum well is only seen if intermediate GaP layers are grown between the GaAs and GaInP and is otherwise masked by anomalous bands at around 1.46 eV. Examination of the TRPL spectra shows large differences in the pressure dependence of this emission because of the inequivalence of the GaAs/GaInP interfaces. For the sample with no thin GaP layer between the upper interface this emission has a very long PL-decay time and a stronger blueshift with excitation intensity at higher pressures. The pressure-dependent PL behavior at lower excitation intensity is close to that of the GaInP barrier. The 1.46 eV emission can be attributed to the spatially indirect transitions at the interface with no GaP layer.

Effect of Pressure on the Anomalous Raman Spectrum of CuBr

Raman spectra of isotopically pure zinc-blende CuBr (63Cu81Br) were measured at T = 10 K under hydrostatic pressures up to 4 GPa. The ambient-pressure spectrum consists of a transverse-optic (TO) phonon line and an anomalous broad band located at frequencies near the expected first-order longitudinal-optic (LO) scattering. Application of hydrostatic pressure leads to an increase of the linewidth of the TO mode and to a significant change of the LO scattering band which above 3 GPa develops into a single LO phonon peak of narrow linewidth. The disappearance of the LO Raman anomaly as well as the broadening of the TO mode with pressure are explained by pressure-dependent third-order anharmonic interactions of zone-center optical phonons with q = 0 two-phonon states.

Temperature effect of infrared rays absorbed by the protein molecules ln the living systems

The principal features of Infrared absorption of the protein molecules are anomalous red shifts of the main peaks and increases of intensity of the anomalous bands with decreasing temperature which are proved by experiments. We think that these anomalous phenomena are caused by the self-trapping of amide-I vibrational quantum (vibron). We thus proposed a soliton model of the vibrons interacting with optical vibration of amino acid residue (phonon) to study theoretically these phenomena. We find farther out the exponential-reductions of the intensity of the anomalous bands in the infrared absorption with increasing temperature in the protein molecules by using this model. This shows that the living things including human beings and animals can absorb more much infrared lights at low temperature than that at high temperature.

Band gap and lattice constant of GaxIn1−xAsySb1−y

The energy band gap and lattice constant of the quaternary alloy GaxIn1−xAsySb1−y were determined over the entire composition space (x, y) using a correlated function expansion (CFE) technique to interpolate from observed ternary compound data. Considerable anomalous band gap behavior (i.e., deep bowing) was found, which produced band gap minima as a function of composition. This deep bowing effect was experimentally observed in a quasibinary alloy (GaSb)1−z(InAs)z at low values of z. In addition, the CFE lattice matching relations of the alloy grown on GaSb and InAs were obtained as a function of composition, and the corresponding band gaps were estimated. The CFE estimates were in good agreement with existing experimental data.

Spectroscopy and photophysics of 1-phenylisatin and oxindole

The absorption and photoluminescence characteristics of 1-phenylisatin (PI) and oxindole (OI) were studied in different solvents at 300 K. In the basic solution a new absorption band system found for PI has been attributed to a structural change leading to formation of new species. Dual fluorescence for PI and OI in different solvents was explained as normal 1B 2u → 1A 1g transition and the other well-structured band as an anomalous band. This large Stokes shifted anomalous band of PI in water and alcohol was explained as fluorescence emission from a state formed due to solute–solvent relaxation producing a sort of critical inversion. Studies in different solvents including a β-cyclodextrin solution revealed that in suitable active medium PI has all the properties to be potential laser dye.

Anomalous surface absorption band at 1.2 eV in Si1−xGex alloy-based structures

An anomalous absorption band was observed around 1.2 eV in Si1−xGex alloy-based structures by photoluminescence excitation spectroscopy and photocurrent measurement. From spectral changes after mechanical lapping and subsequent air-borne annealing, it is found that the 1.2 eV absorption band develops only after oxidation of the alloy surface. The 1.2eV band survived up to 240 K in photocurrent measurements, which promises a wavelength selective detector operating near room temperature.

Organization of the pigment molecules in the chlorophyll a/b/c containing alga Mantoniella squamata (Prasinophyceae) studied by means of absorption, circular and linear dichroism spectroscopy

In order to obtain information on the organization of the pigment molecules in chlorophyll (Chl) a/b/c-containing organisms, we have carried out circular dichroism (CD), linear dichroism (LD) and absorption spectroscopic measurements on intact cells, isolated thylakoids and purified light-harvesting complexes (LHCs) of the prasinophycean alga Mantoniella squamata. The CD spectra of the intact cells and isolated thylakoids were predominated by the excitonic bands of the Chl a/b/c LHC. However, some anomalous bands indicated the existence of chiral macrodomains, which could be correlated with the multilayered membrane system in the intact cells. In the red, the thylakoid membranes and the LHC exhibited a well-discernible CD band originating from Chl c, but otherwise the CD spectra were similar to that of non-aggregated LHC II, the main Chl a/b LHC in higher plants. In the Soret region, however, an unusually intense (+) 441 nm band was observed, which was accompanied by negative bands between 465 and 510 nm. It is proposed that these bands originate from intense excitonic interactions between Chl a and carotenoid molecules. LD measurements revealed that the Q Y dipoles of Chl a in Mantoniella thylakoids are preferentially oriented in the plane of the membrane, with orientation angles tilting out more at shorter than at longer wavelengths (9° at 677 nm, 20° at 670 nm and 26° at 662 nm); the Q Y dipole of Chl c was found to be oriented at 29° with respect to the membrane plane. These data and the LD spectrum of the LHC, apart from the presence of Chl c, suggest an orientation pattern of dipoles similar to those of higher plant thylakoids and LHC II. However, the tendency of the Q Y dipoles of Chl b to lie preferentially in the plane of the membrane (23° at 653 nm and 30° at 646 nm) is markedly different from the orientation pattern in higher plant membranes and LHC II. Hence, our CD and LD data show that the molecular organization of the Chl a/b/c LHC, despite evident similarities, differs significantly from that of LHC II.

Supersonic jet and solution studies of intramolecular complexes with TICT formation mimicking solute–solvent interaction

Three ester derivatives of N, N-dimethylaniline have been studied, which possess a flexibly linked intramolecular hydroxyl group amenable to mimic 1:1 complexation of donor–acceptor molecules with solvent molecules. The supersonic jet fluorescence excitation spectra indicate a small redshift for these intramolecularly complexed compounds with respect to the noncomplexed model compounds giving evidence for the intramolecular complexation by hydrogen bond formation at the ester group. The dispersed fluorescence spectra broaden upon an increase in the excitation energy. Semiempirical simulated annealing calculations using AMPAC/AM1 show that there exist many possible conformations of similar energy for the molecule, with H bonding at the carbonyl or alkoxy oxygen in the most stable conformer. A shift in the carbonyl vibrational frequencies is consistent with a carbonyl self-complexed species. The dual fluorescence observed in acetonitrile as solvent is very similar for all three compounds, with a slight redshift of the long wavelength charge transfer (CT) band for the complexed species with respect to the uncomplexed one consistent with the twisted intramolecular charge transfer model. The absence of a clear CT band in spite of complete intramolecular hydrogen bond complexation in alkanes is interpreted as evidence that formation of a specific solute–solvent complex alone is not sufficient to create the large anomalous CT band observed for N, N-dimethylaminobenzonitrile in polar and mixed polar/nonpolar solvents.