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1.
Struct Dyn ; 3(2): 023601, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26798832

RESUMO

Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns). We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs) passage through a CoIn. This is demonstrated by a multiconfigurational self-consistent-field study of the dynamics and spectroscopy of the furan ring-opening reaction. Trajectories generated by surface hopping simulations were used to predict Attosecond Stimulated X-ray Raman Spectroscopy signals at reactant and product structures as well as representative snapshots along the conical intersection seam. The signals are highly sensitive to the changes in nonadiabatically coupled electronic structure and geometry.

2.
J Chem Phys ; 142(2): 024115, 2015 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-25591346

RESUMO

Electron and vibrational dynamics of molecules are commonly studied by subjecting them to two interactions with a fast actinic pulse that prepares them in a nonstationary state and after a variable delay period T, probing them with a Raman process induced by a combination of a broadband and a narrowband pulse. This technique, known as femtosecond stimulated Raman spectroscopy (FSRS), can effectively probe time resolved vibrational resonances. We show how FSRS signals can be modeled and interpreted using the stochastic Liouville equations (SLE), originally developed for NMR lineshapes. The SLE provide a convenient simulation protocol that can describe complex dynamics caused by coupling to collective bath coordinates at much lower cost than a full dynamical simulation. The origin of the dispersive features that appear when there is no separation of timescales between vibrational variations and the dephasing time is clarified.


Assuntos
Modelos Teóricos , Análise Espectral Raman , Processos Estocásticos , Fatores de Tempo
3.
J Am Chem Soc ; 136(42): 14801-10, 2014 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-25238196

RESUMO

Cyclobutane thymine dimer, one of the major lesions in DNA formed by exposure to UV sunlight, is repaired in a photoreactivation process, which is essential to maintain life. The molecular mechanism of the central step, i.e., intradimer C-C bond splitting, still remains an open question. In a simulation study, we demonstrate how the time evolution of characteristic marker bands (C═O and C═C/C-C stretch vibrations) of cyclobutane thymine dimer and thymine dinucleotide radical anion, thymidylyl(3'→5')thymidine, can be directly probed with femtosecond stimulated Raman spectroscopy (FSRS). We construct a DFT(M05-2X) potential energy surface with two minor barriers for the intradimer C5-C5' splitting and a main barrier for the C6-C6' splitting, and identify the appearance of two C5═C6 stretch vibrations due to the C6-C6' splitting as a spectroscopic signature of the underlying bond splitting mechanism. The sequential mechanism shows only absorptive features in the simulated FSRS signals, whereas the fast concerted mechanism shows characteristic dispersive line shapes.


Assuntos
Reparo do DNA , Dímeros de Pirimidina/química , Análise Espectral Raman , Radicais Livres/química , Modelos Moleculares , Conformação Molecular , Dímeros de Pirimidina/metabolismo , Teoria Quântica , Termodinâmica , Fatores de Tempo
4.
J Am Chem Soc ; 134(11): 5083-9, 2012 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-22364147

RESUMO

A quasielastic neutron scattering and solid-state (2)H NMR spectroscopy study of the polymeric spin-crossover compound {Fe(pyrazine)[Pt(CN)(4)]} shows that the switching of the rotation of a molecular fragment--the pyrazine ligand--occurs in association with the change of spin state. The rotation switching was examined on a wide time scale (10(-13)-10(-3) s) by both techniques, which clearly demonstrated the combination between molecular rotation and spin-crossover transition under external stimuli (temperature and chemical). The pyrazine rings are seen to perform a 4-fold jump motion about the coordinating nitrogen axis in the high-spin state. In the low-spin state, however, the motion is suppressed, while when the system incorporates benzene guest molecules, the movements of the system are even more restricted.

6.
Dalton Trans ; 39(7): 1836-45, 2010 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-20449430

RESUMO

We investigated mer- and fac-[Fe(II)(2-pic)(3)](2+) (pic = picolylamine) and Fe(iii) analogue, mer-[Fe(III)(2-pic)(3)](3+), by the DFT method to clarify the mechanism of light-induced excited spin state trapping (LIESST). In mer-[Fe(II)(2-pic)(3)](2+), the potential energy surface (PES) of the triplet state is the least stable but it is close to the PESs of the singlet and quintet states at the equilibrium geometry of the triplet state within 5 kcal mol(-1). This indicates that intersystem crossing occurs from the triplet state to either the singlet state or the quintet state around the equilibrium geometry of the triplet state. The quintet state is as stable as the singlet state in their equilibrium geometries. All Fe-N bonds of the quintet state are longer than those of the singlet state by about 0.19 A. These are consistent with the general understanding that the Fe-ligand distances are considerably different but the relative stability is little different between the low spin and high spin states in LIESST complexes. Actually, a large activation barrier is calculated for the conversion between the singlet and quintet states, which is enough to suppress thermal spin transition and tunneling between them. The d-d transition energies are calculated with the TD-DFT method to be 2.05, 2.07, and 2.09 eV in the singlet state and 1.46 and 1.64 eV in the quintet state. Because of the significantly large difference in excitation energy between the singlet and quintet states, irradiation of visible light with different wavelengths selectively induces the excitation to the singlet excited state or the quintet one. All these results are consistent with the fact that both LIESST and reverse-LIESST are observed in mer-[Fe(II)(2-pic)(3)](2+). The fac-isomer is also useful for the LIESST/reverse-LIESST, though the mer-isomer is better. In the Fe(iii) analogue, mer-[Fe(III)(2-pic)(3)](3+), the DFT-computational results indicate small activation barriers and a large overlap of absorption spectra between the doublet and sextet states. Also, the Fe(III)-N bond distances are less different between the low spin and high spin states than the Fe(II)-N ones, leading to the narrow potential wall between the doublet and sextet states. As a result, the LIESST and reverse-LIESST cannot be observed in this Fe(iii) complex.


Assuntos
Elétrons , Compostos Férricos/química , Luz , Simulação por Computador , Modelos Químicos , Estrutura Molecular
7.
Undersea Hyperb Med ; 37(1): 7-11, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20369648

RESUMO

We report on a Japanese male professional breath-hold diver (Ama) who developed neurological disorders during repetitive dives to 22 meters of sea water. Each diving duration and surface interval were 40-80 seconds and 20-30 seconds, respectively. He suffered from sensory numbness of the right cheek, hand and foot, and double vision after more than two hours of consecutive dives. Magnetic resonance images of his brain showed multiple cerebral infarcts, and one of the lesions was situated in the brainstem. There is a possibility that repetitive deep breath-hold dives with short surface intervals can induce fatal accidents for divers.


Assuntos
Infarto Cerebral/etiologia , Mergulho/efeitos adversos , Adulto , Doenças Cerebelares/etiologia , Infarto Cerebral/diagnóstico , Infarto Cerebral/terapia , Doença da Descompressão/etiologia , Doença da Descompressão/terapia , Humanos , Oxigenação Hiperbárica , Imagem por Ressonância Magnética , Masculino , Parestesia/etiologia , Parestesia/terapia , Respiração , Fatores de Tempo
8.
Angew Chem Int Ed Engl ; 48(26): 4767-71, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19294711

RESUMO

The ins and outs of spin: Using the microporous coordination polymer {Fe(pz)[Pt(CN)(4)]} (1, pz=pyrazine), incorporating spin-crossover subunits, two-directional magnetic chemo-switching is achieved at room temperature. In situ magnetic measurements following guest vapor injection show that most guest molecules transform 1 from the low-spin (LS) state to the high-spin (HS) state, whereas CS(2) uniquely causes the reverse HS-to-LS transition.

9.
Kurume Med J ; 56(1-2): 17-23, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-20103997

RESUMO

The purpose of this study was to clarify the influence of different vibration frequencies on wakefulness level. Subjects were 7 healthy male university students aged 21.9+/-1.6 years (mean). All students were non-smokers. Three exposure conditions were used (10 Hz vibration, 20 Hz vibration, and no vibration). Whole-body vertical vibration was applied to subjects sitting on a car passenger seat using a whole-body vibration shaker (CV-300, Akashi) at a single frequency (10 or 20 Hz) at an acceleration level of 0.3 ms(-2) r.m.s. for 24 min. The objective wakefulness level based on EEGs was evaluated in terms of the alpha attenuation coefficient (AAC) obtained by the Alpha Attenuation Test (AAT). As parameters of psychological stress, salivary 3-methoxy-4-hydroxyphenylglycol (MHPG) and homovanillic acid (HVA) were used. The subjective wakefulness level was evaluated using a questionnaire based on the Kwansei Gakuin Sleepiness Scale (KSS), which is a scale developed for the Japanese based on the Stanford Sleepiness Scale (SSS). The KSS score, representing the subjective wakefulness level, decreased after the exposure irrespective of the exposure condition, but the decrease was not significant. The AAC, representing the objective wakefulness level, significantly decreased only after vibration exposure (10 Hz/20 Hz) but did not differ between the two vibration frequencies. No significant changes were observed after exposure to whole-body vibration in MHPG or HVA as parameters of vibration-related stress. The AAC decreased after exposure to whole-body vibration (10 Hz/20 Hz), suggesting a decrease in the wakefulness level. However, no differences were observed in the influence of the two different vibration frequencies test.


Assuntos
Vibração , Vigília , Adulto , Eletroencefalografia , Ácido Homovanílico/análise , Humanos , Masculino , Metoxi-Hidroxifenilglicol/análise , Saliva/química
10.
J Phys Chem A ; 111(25): 5515-22, 2007 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-17547380

RESUMO

The mechanism of light-induced excited spin state trapping (LIESST) of [FeIII(pap)2]+ (pap = N-2-pyridylmethylidene-2-hydroxyphenylaminato) was discussed on the basis of potential energy surfaces (PESs) of several important spin states, where the PESs were evaluated with the DFT(B3LYP) method. The PES of the quartet spin state crosses those of the doublet and sextet spin states around its minimum. This means that the spin transition occurs from the quartet spin state to either the doublet spin state or the sextet spin state around the PES minimum of the quartet spin state. The PES minimum of the sextet spin state is slightly less stable than that of the doublet spin state by 0.18 eV (4.2 kcal/mol). This small energy difference is favorable for the LIESST. The doublet-sextet spin crossover point is 0.41 eV (9.6 kcal/mol) above the PES minimum of the sextet spin state. Because of this considerably large activation barrier, the thermal spin transition and the tunneling process do not occur easily. In the doublet spin state, the ligand to ligand charge transfer (LLCT) transition is calculated to be 2.16 eV with the TD-DFT(B3LYP) method, in which the pi orbital of the phenoxy moiety and the pi* orbital of the imine moiety in the pap ligand participate. This transition energy is moderately smaller than the visible light of 550 nm used experimentally. In the sextet spin state, the ligand to metal charge transfer (LMCT) transition is calculated to be at 2.36 eV, which is moderately higher than the visible light (550 nm). These results indicate that the irradiation of the visible light induces the LIESST to generate the sextet spin state but the reverse-LIESST is also somewhat induced by the visible light, indicating that the complete spin conversion from the doublet spin state to the sextet one does not occur, as reported experimentally.

11.
Ind Health ; 45(2): 217-23, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17485865

RESUMO

To investigate the relationships between whole-body vibration and changes in wakefulness, We measured the change of a subjective wakefulness level and electroencephalogram (EEG). Subjects are ten healthy male university students. The subjects were exposed to whole-body vibration with frequency (10 Hz) and acceleration level (0.6 ms(-2) r.m.s.) for 12 min in the seated position. Subjective wakefulness level was evaluated using the questionnaire of VASS (Visual Analog Sleepiness Scale) and KSS (The Kwansei Gakuin Sleepiness Scale). For the electroencephalogram (EEG) measurement, AAT (Alpha Attenuation Test) which repeats three times each opened and closed eye for 1 min was conducted. Wakefulness levels were defined as the ratio of mean alpha-wave power during eyes closed versus eyes opened. VASS and KSS increased and subjective level of wakefulness decreased from pre- to post exposure in all subjects, regardless of vibration exposure. The objective wakefulness levels of AAT were reduced at the post-exposure test in all subjects. In the case with exposure to whole-body vibration was a significant difference from the case without exposure to whole-body vibration. It is suggested that a short-term exposure to whole-body vibration may cause a reduction of wakefulness level.


Assuntos
Eletroencefalografia , Polissonografia/métodos , Vibração/efeitos adversos , Vigília/fisiologia , Adulto , Estudos de Casos e Controles , Humanos , Japão , Masculino , Medição da Dor , Percepção , Polissonografia/instrumentação , Inquéritos e Questionários
12.
Scand J Work Environ Health ; 31(4): 286-90, 2005 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16161711

RESUMO

OBJECTIVES: This study was carried out to evaluate the damage induced in red blood cells by exposure to impulse vibration. METHODS: The peak accelerations of impulse vibration included 50, 100, 200, 250 and 300 x 10(3) km/s2. A blood sample was put in a container filled with heparin so that there was no space inside. For each peak acceleration the exposure durations of 10, 20, and 30 minutes were used. The repetition rate of the impulses was 1 cycle per second (1 cycle/s). After the vibration exposure, the percentage of damaged red blood cells was calculated. Then the red blood cells were studied microscopically. RESULTS: Each vibration caused damage to red blood cells with all durations. The higher the peak acceleration and the longer the exposure duration, the more the damage to the red blood cells. Of the five impulse vibration levels with the three exposure durations, the largest damage was done by the vibration exposure with a peak acceleration of 300 km/s2 for 30 minutes with a mean value of 76.7% for the damaged cells, followed by the exposure with a peak acceleration of 300 km/s2 for 20 minutes with 55.5% of the cells being damaged. For exposure for 20 and 30 minutes, the vibration with peak accelerations of higher than 200 km/s2 provoked damage to red blood cells out of proportion to those with peak accelerations lower than 200 km/s2. CONCLUSIONS: Impulse vibration was shown in vitro to cause damage to red blood cells. It is suggested that the damage of red blood cells depends on both the peak acceleration and exposure duration of impulse vibration.


Assuntos
Eritrócitos , Vibração/efeitos adversos , Humanos , Técnicas In Vitro
13.
Environ Health Prev Med ; 10(6): 371-5, 2005 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21432122

RESUMO

OBJECTIVES: To evaluate the relationship between subjective symptoms of coldness in fingers and peripheral circulation in patients with hand-arm vibration syndrome (HAVS). METHODS: Thirty-five male patients confirmed to have HAVS as an occupational disease took part in this study. Their mean age was 62 years (SD 5) and all were chain-saw operators exposed to vibration for an average of 25 years. Their annual health examination included the history of their daily habits (smoking, drinking, and therapeutic exercise), report of subjective symptoms such as coldness, numbness and tingling in the fingers, and a physical examination; laboratory tests consisted of skin temperature measurement, and pain and vibration perception under conditions of cold provocation. A frequently used method of cold provocation, immersion of the left hand up to the wrist in water of 10°C for 10 min, was used. RESULTS: Finger coldness was classified into 3 groups according to its severity: mild group (n=8), moderate group (n=17) and severe group (n=10). There was no significant difference in age or occupational background between the groups. A significant association was found between finger coldness and prevalence of Raynaud's pheno menon (p<001, χ(2)). The mean skin temperature was significantly lower with the severity of finger coldness (ANOVA, p<0.05). In the cold provocation test, there was no significant difference between skin temperature and coldness at 5 min and 10 min after immersion, though a difference was observed immediately after immersion. No significant difference was observed in the relationship between finger coldness and vibrotactile threshold before, during or after the cold provocation test. CONCLUSIONS: The severity of coldness in the fingers is significantly related to skin temperature. The severity of finger coldness reflects the extent of peripheral circulatory vasoconstriction. Coldness in the fingers may be a good warning of potential problems in peripheral, circulatory function.

14.
Scand J Work Environ Health ; 29(3): 216-9, 2003 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12828391

RESUMO

OBJECTIVES: This study was carried out to determine the effects of the frequency of whole-body vibration on palmar sweating response and the activity of the central sympathetic nervous system. METHODS: Palmar sweating volume was measured on the right palm of six healthy men before and during 3 minutes of exposure to sinusoidal whole-body vibration at three different frequencies (16, 31.5, and 63 Hz). The whole-body vibration had a frequency-weighted, root mean square (rms) acceleration magnitude of 2.0 m/s2. As the index of the activated central sympathetic nervous system, saliva level of 3-methoxy-4-hydroxyphenylglycol (MHPG) was analyzed before and immediately after each vibration exposure. RESULTS: Each vibration frequency induced a palmar sweating response, that of 31.5 Hz being the largest. However, no significant difference was found between the three vibration conditions. Saliva MHPG increased in all the vibration exposures, and the largest change was observed at 31.5 Hz, the difference being significant. CONCLUSIONS: Acute exposure to whole-body vibration induced a palmar sweating response and activated the central sympathetic nervous system. The effects on the central nervous system were found to be dependent on the frequency of the vibration.


Assuntos
Sistema Nervoso Central/fisiologia , Mãos/fisiologia , Glândulas Sudoríparas/metabolismo , Sudorese/fisiologia , Vibração , Adulto , Humanos , Masculino , Metoxi-Hidroxifenilglicol/isolamento & purificação , Exposição Ocupacional/análise , Saliva/fisiologia , Estresse Fisiológico/fisiopatologia
15.
Kurume Med J ; 49(3): 87-9, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12471722

RESUMO

The aim of the experiments was to observe whether or not there is an immune system reaction to vibration stress. Three vibration frequencies were randomly given to 6 male volunteers. The 63 Hz vibration frequency produced a significant decrease in the ratio of CD4 T-cell to CD8 T-cell. This finding suggests that acute vibration stress suppresses the immune system activity in humans body.


Assuntos
Relação CD4-CD8 , Estresse Psicológico/imunologia , Vibração , Adulto , Humanos , Masculino
16.
Scand J Work Environ Health ; 28(5): 324-7, 2002 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-12432985

RESUMO

OBJECTIVES: This study attempted to elucidate the effects of hand-arm vibration frequency on palmar sweating response. METHODS: Palmar sweating was measured before and during vibration exposure on the right palm of six healthy men. The left hand was exposed for 3 minutes to the following root mean square (rms) acceleration magnitudes and frequencies of vibration: 5 m/s2 at 31.5 Hz, 10 m/s2 at 63 Hz, 20 m/s2 at 125 Hz, 40 m/s2 at 250 Hz, and 50 m/s2 at 315 Hz. According to international standard ISO 5349, these vibration levels generate the same frequency-weighted acceleration magnitude of 2.5 m/s2 rms. A control condition consisted of grasping a handle without vibration. As the index of the activated central nervous system, plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) was measured before and immediately after each vibration exposure. RESULTS: Each condition of vibration induced a palmar sweating response. Among the six vibration conditions, vibration of 125 Hz and 63 Hz caused large palmar sweating responses compared with those of 315 Hz andthe control condition. Plasma MHPG did not increase significantly after either vibrationexposure. CONCLUSIONS: The palmar sweating response to vibration with the same frequency-weightedacceleration magnitude suggested dependency on frequency. The study suggests that the somatosympathetic reflex is associated with different palmar sweating responses.


Assuntos
Mãos/fisiologia , Exposição Ocupacional/efeitos adversos , Sudorese/fisiologia , Vibração/efeitos adversos , Adulto , Análise de Variância , Braço , Humanos , Masculino
17.
Eur J Appl Physiol ; 87(4-5): 315-7, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12172868

RESUMO

We investigated the effect of cold ambient temperature on the palmar sweating response to vibration stress. Ten healthy, male subjects were exposed to eight ambient temperatures (5, 7, 10, 14, 18, 22, 24 and 28 degrees C). At each ambient temperature, each subject gripped the handle of a vibration generator with his left hand with a grasp strength of 49 N. This hand was then exposed to a 125-Hz sinusoidal vibration with an acceleration of 50 m/s(2) (rms) for 3 min at each ambient temperature. Palmar sweating and skin temperature were measured simultaneously on the palm and the fourth finger, respectively, of the subjects' right palm. The palmar sweating response showed a significant change among eight ambient temperatures. The palmar sweating measured at an ambient temperature of 5 degrees C was found to be significantly larger than those measured at 10, 14, 18, 22, 24 and 28 degrees C. Vibration exposure caused a significant increase in the palmar sweating response. Our results suggest that a cold environment plays a significant role in the palmar sweating response to vibration stress.


Assuntos
Temperatura Baixa , Mãos/fisiopatologia , Estresse Fisiológico/etiologia , Estresse Fisiológico/fisiopatologia , Sudorese , Vibração/efeitos adversos , Adulto , Humanos , Masculino
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