Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 43
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
J Chem Phys ; 151(12): 124305, 2019 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-31575189

RESUMO

We performed reaction dynamics simulations to demonstrate that the vibrational dynamics of C60 induced by infrared (IR) pulses can be traced by triggering Coulomb explosion with intense femtosecond X-ray free electron laser (XFEL) probe pulses. The time series of the angular anisotropy ß(t) of fast C+ and C2+ fragments of C60 60+ produced by such an XFEL pulse reflects the instantaneous structure of C60 vibrationally excited by IR pulses. The phases and amplitudes of excited vibrational modes and the coupling between excited modes can be successfully extracted from the expansion of ß(t) in terms of vibrational modes. This proof-of-principle simulation clearly demonstrates that various information of the structures and reaction dynamics of large clusters or biomolecules can be retrieved by decomposing the experimentally determined ß(t) into vibrational modes.

3.
Phys Chem Chem Phys ; 21(36): 19755-19763, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31259349

RESUMO

The electronic states and photochemistry including nonradiative decay (NRD) and trans(E) → cis(Z) isomerization of methylcinnamate (MC) and its hydrogen-bonded complex with methanol have been investigated under jet-cooled conditions. S1(1nπ*) and S2(1ππ*) are directly observed in MC. This is the first direct observation of S1(1nπ*) in cinnamate derivatives. Surprisingly, the order of the energies between the nπ* and ππ* states is opposite to substituted cinnamates. TD-DFT and SAC-CI calculations support the observed result and show that the substitution to the benzene ring largely lowers the 1ππ* energy while the effect on 1nπ* is rather small. The S2(ππ*) state lifetime of MC is determined to be equal to or shorter than 10 ps, and the production of the transient T1 state is observed. The T1(ππ*) state is calculated to have a structure in which propenyl C[double bond, length as m-dash]C is twisted by 90°, suggesting the trans → cis isomerization proceeds via T1. The production of the cis isomer is confirmed by low-temperature matrix-isolated FTIR spectroscopy. The effect of H-bonding is examined for the MC-methanol complex. The S2 lifetime of MC-methanol is determined to be 180 ps, indicating that the H-bonding to the C[double bond, length as m-dash]O group largely prohibits the 1ππ* → 1nπ* internal conversion. This lifetime elongation in the methanol complex also describes well a higher fluorescence quantum yield of MC in methanol solution than in cyclohexane, while such a solvent dependence is not observed in para-substituted MC. Determination of the photochemical reaction pathways of MC and MC-methanol will help us to design photofunctional cinnamate derivatives.

4.
Nat Commun ; 10(1): 2186, 2019 05 16.
Artigo em Inglês | MEDLINE | ID: mdl-31097703

RESUMO

The increasing availability of X-ray free-electron lasers (XFELs) has catalyzed the development of single-object structural determination and of structural dynamics tracking in real-time. Disentangling the molecular-level reactions triggered by the interaction with an XFEL pulse is a fundamental step towards developing such applications. Here we report real-time observations of XFEL-induced electronic decay via short-lived transient electronic states in the diiodomethane molecule, using a femtosecond near-infrared probe laser. We determine the lifetimes of the transient states populated during the XFEL-induced Auger cascades and find that multiply charged iodine ions are issued from short-lived (∼20 fs) transient states, whereas the singly charged ones originate from significantly longer-lived states (∼100 fs). We identify the mechanisms behind these different time scales: contrary to the short-lived transient states which relax by molecular Auger decay, the long-lived ones decay by an interatomic Coulombic decay between two iodine atoms, during the molecular fragmentation.

5.
Mov Disord Clin Pract ; 6(3): 213-221, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30949552

RESUMO

Background: Postural abnormalities in Parkinson's disease (PD) patients and unimpaired elderly are not well differentiated. Factors related to postural abnormality associated with PD are controversial. Objective: We assessed differences in postural change between PD patients and unimpaired elderly and elucidated factors related to abnormal posture in PD patients. Methods: We measured the dropped head angle (DHA), anterior flexion angle (AFA), and lateral flexion angle (LFA) of the thoracolumbar spine of an unprecedented 1,117 PD patients and 2,732 general population participants (GPPs) using digital photographs. Two statistical analyses were used for elucidating factors related to these angles. Results: In GPPs, age was correlated with DHA, AFA, and LFA. DHAs, AFAs, and LFAs of PD patients and age-matched GPPs were 21.70° ± 14.40° and 13.13° ± 10.79°, 5.98° ± 12.67,°and - 3.82° ± 4.04°, and 0.86° ± 4.25° and 1.33° ± 2.16°, respectively. In PD patients, factors related to DHA were age, male sex, and H & Y stage during ON time. Factors related to AFA were age, duration of disease, H & Y stage during ON and OFF times, pain, vertebral disease, and bending to the right. A factor related to LFA was AFA. Conclusions: DHA and AFA of GGPs correlated with age and were larger in PD patients than those with in GPPs. Some PD patients showed angles far beyond the normal distribution. Thus, factors associated with disease aggravation affected postural abnormality in PD patients.

6.
Phys Rev Lett ; 122(5): 053002, 2019 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-30822022

RESUMO

Theoretical studies indicated that C_{60} exposed to linearly polarized intense infrared pulses undergoes periodic cage structural distortions with typical periods around 100 fs (1 fs=10^{-15} s). Here, we use the laser-driven self-imaging electron diffraction technique, previously developed for atoms and small molecules, to measure laser-induced deformation of C_{60} in an intense 3.6 µm laser field. A prolate molecular elongation along the laser polarization axis is determined to be (6.1±1.4)% via both angular- and energy-resolved measurements of electrons that are released, driven back, and diffracted from the molecule within the same laser field. The observed deformation is confirmed by density functional theory simulations of nuclear dynamics on time-dependent adiabatic states and indicates a nonadiabatic excitation of the h_{g}(1) prolate-oblate mode. The results demonstrate the applicability of laser-driven electron diffraction methods for studying macromolecular structural dynamics in four dimensions with atomic time and spatial resolutions.

7.
J Phys Chem Lett ; 9(24): 6927-6933, 2018 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-30444124

RESUMO

Ultrafast XUV chemistry is offering new opportunities to decipher the complex dynamics taking place in highly excited molecular states and thus better understand fundamental natural phenomena as molecule formation in interstellar media. We used ultrashort XUV light pulses to perform XUV pump-IR probe experiments in caffeine as a model of prebiotic molecule. We observed a 40 fs decay of excited cationic states. Guided by quantum calculations, this time scale is interpreted in terms of a nonadiabatic cascade through a large number of highly correlated states. This shows that the correlation driven nonadiabatic relaxation seems to be a general process for highly excited states, which might impact our understanding of molecular processing in interstellar media.

8.
Phys Chem Chem Phys ; 20(26): 17583-17598, 2018 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-29693100

RESUMO

An experimental and theoretical study has been carried out to elucidate the nonradiative decay (NRD) and trans(E) → cis(Z) isomerization from the S1 (1ππ*) state of structural isomers of hydroxy methylcinnamate (HMC); ortho-, meta- and para-HMC (o-, m- and p-HMC). A low temperature matrix-isolation Fourier Transform Infrared (FTIR) spectroscopic study revealed that all the HMCs are cis-isomerized upon UV irradiation. A variety of laser spectroscopic methods have been utilized for jet-cooled gas phase molecules to investigate the vibronic structure and lifetimes of the S1 state, and to detect the transient state appearing in the NRD process. In p-HMC, the zero-point level of the S1 state decays as quickly as 9 ps. A transient electronic state reported by Tan et al. (Faraday Discuss. 2013, 163, 321-340) was reinvestigated by nanosecond UV-tunable deep UV pump-probe spectroscopy and was assigned to the T1 state. For m- and o-HMC, the lifetime at the zero-point energy level of S1 is 10 ns and 6 ns, respectively, but it becomes substantially shorter at an excess energy higher than 1000 cm-1 and 600 cm-1, respectively, indicating the onset of NRD. Different from p-HMC, no transient state (T1) was observed in m- nor o-HMC. These experimental results are interpreted with the aid of TDDFT calculations by considering the excited-state reaction pathways and the radiative/nonradiative rate constants. It is concluded that in p-HMC, the trans → cis isomerization proceeds via a [trans-S1 → 1nπ* → T1 → cis-S0] scheme. On the other hand, in o- and m-HMC, the isomerization proceeds via a [trans-S1 → twisting along the C[double bond, length as m-dash]C double bond by 90° on S1 → cis-S0] scheme. The calculated barrier height along the twisting coordinate agrees well with the observed onset of the NRD channel for both o- and m-HMC.

9.
J Med Ultrason (2001) ; 45(1): 15, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28933006

RESUMO

In the original version of the article, the third author name was incorrectly published. The correct name is Kosei Yoh.

10.
J Med Ultrason (2001) ; 45(1): 3-13, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28884290

RESUMO

Dual X-ray absorptiometry (DXA) is used to diagnose osteoporosis. On the other hand, quantitative ultrasound (QUS) is widely used to assess bone density as part of medical screening as it is relatively inexpensive and easy to perform. Current QUS devices do not share precise ultrasound-related parameters, such as frequency, waveform, beam pattern, transient response, definition of propagation time, definition of degree of attenuation, and precise measurement site, resulting in different measurements across models. The Japan Osteoporosis Society established a QUS Standardization Committee in 2007 to investigate standardization of speed of sound (SOS) and broadband ultrasonic attenuation (BUA) measurements to resolve this issue. The committee came up with a formula to convert SOS and BUA values yielded by each model available in Japan. This has made it possible to convert QUS measurements from different models into standardized values, greatly improving the effectiveness of QUS measurements.


Assuntos
Densidade Óssea , Osso e Ossos/diagnóstico por imagem , Osteoporose/diagnóstico por imagem , Ultrassonografia/normas , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Japão , Masculino , Pessoa de Meia-Idade , Padrões de Referência , Valores de Referência , Ondas Ultrassônicas , Ultrassonografia/instrumentação , Ultrassonografia/métodos , Adulto Jovem
11.
Breed Sci ; 67(3): 320-326, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28744186

RESUMO

'Nagasaki Kogane' is a new potato variety bred from a cross between 'Saikai 35' as a female parent and 'Saikai 33' as a male. 'Saikai 35' is resistant to bacterial wilt, contains the H1 and Rychc genes for resistance to the potato cyst nematode (PCN) and potato virus Y (PVY), respectively, and has high carotenoid content, while 'Saikai 33' has large and high-yielding tubers and is resistant to both bacterial wilt and PCN. The carotenoid content of 'Nagasaki Kogane' is higher than that of 'Dejima', a common double cropping variety. The taste quality of steamed 'Nagasaki Kogane' is comparable to that of 'Inca-no-mezame' tubers, which has high levels of carotenoid, and superior to 'Nishiyutaka', another popular double cropping variety. 'Nagasaki Kogane' is suitable for French fries, because its tuber has high starch content. The marketable yield of 'Nagasaki Kogane' was higher than that of 'Inca-no-mezame' in spring cropping, although it was lower than that of 'Nishiyutaka' in double cropping regions. 'Nagasaki Kogane' tubers are larger on average than 'Inca-no-mezame' tubers in spring cropping. Moreover, the 'Nagasaki Kogane' variety is resistant to PCN and PVY, and exhibits a high level of resistance to bacterial wilt.

12.
Phys Chem Chem Phys ; 19(30): 19707-19721, 2017 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-28530728

RESUMO

Coulomb explosion of diiodomethane CH2I2 molecules irradiated by ultrashort and intense X-ray pulses from SACLA, the Japanese X-ray free electron laser facility, was investigated by multi-ion coincidence measurements and self-consistent charge density-functional-based tight-binding (SCC-DFTB) simulations. The diiodomethane molecule, containing two heavy-atom X-ray absorbing sites, exhibits a rather different charge generation and nuclear motion dynamics compared to iodomethane CH3I with only a single heavy atom, as studied earlier. We focus on charge creation and distribution in CH2I2 in comparison to CH3I. The release of kinetic energy into atomic ion fragments is also studied by comparing SCC-DFTB simulations with the experiment. Compared to earlier simulations, several key enhancements are made, such as the introduction of a bond axis recoil model, where vibrational energy generated during charge creation processes induces only bond stretching or shrinking. We also propose an analytical Coulomb energy partition model to extract the essential mechanism of Coulomb explosion of molecules from the computed and the experimentally measured kinetic energies of fragment atomic ions by partitioning each pair Coulomb interaction energy into two ions of the pair under the constraint of momentum conservation. Effective internuclear distances assigned to individual fragment ions at the critical moment of the Coulomb explosion are then estimated from the average kinetic energies of the ions. We demonstrate, with good agreement between the experiment and the SCC-DFTB simulation, how the more heavily charged iodine fragments and their interplay define the characteristic features of the Coulomb explosion of CH2I2. The present study also confirms earlier findings concerning the magnitude of bond elongation in the ultrashort X-ray pulse duration, showing that structural damage to all but C-H bonds does not develop to a noticeable degree in the pulse length of ∼10 fs.

13.
J Phys Chem Lett ; 7(19): 4001-4007, 2016 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-27657500

RESUMO

The nonradiative decay pathways of jet-cooled para-methoxy methylcinnamate (p-MMC) and para-methoxy ethylcinnamate (p-MEC) have been investigated by picosecond pump-probe and nanosecond UV-Deep UV pump-probe spectroscopy. The possible relaxation pathways were calculated by the (time-dependent) density functional theory. We found that p-MMC and p-MEC at low excess energy undergo multistep intersystem crossing (ISC) from the bright S1 (1ππ*) state to the lowest triplet T1 (3ππ*) state via two competing pathways through the T2 state in the time scale of 100 ps: (a) stepwise ISC followed after the internal conversion (IC) from S1 to the dark 1nπ* state; (b) direct ISC from the S1 to T2 states. These picosecond multistep ISCs result in the torsion of C═C double bond by ∼95° in the T1 state, whose measured adiabatic energy and lifetime are 16577 cm-1 and ∼20 ns, respectively, for p-MMC. These results suggest that the ISC processes play an indispensable role in the photoprotecting sunscreens in natural plants.

14.
Clin Nutr ; 35(4): 943-9, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-26216195

RESUMO

BACKGROUND & AIMS: Elderly patients can be at risk of protein catabolism and malnutrition in the early postoperative period. Whey protein includes most essential amino acids and stimulates the synthesis of muscle protein. The purpose of this study was to investigate the effect of resistance training in combination with whey protein intake in the early postoperative period. METHODS: We randomized patients to a whey protein group or a control group. The former group received 32.2 g of whey protein pre- and post-rehabilitation in the early postoperative period for two weeks. Outcomes were knee extension strength on either side by Biodex 4.0, and the ability of transfer, walking, toilet use and stair use by the Barthel Index (BI). We performed initial and final assessments in the second and tenth rehabilitation sessions. RESULTS: A total of 38 patients were recruited: 20 in the whey protein group and 18 in the control group. Participants in the whey protein group showed significantly greater improvement in knee extension strength in the operated limb compared with the control group (F = 6.11, P = 0.02). The non-operated limb also showed a similar tendency (F = 3.51, P = 0.07). The abilities of transfer, walking and toilet use showed greater improvements in the whey protein group than in the control group by BI (P < 0.05). CONCLUSION: The combination of whey protein intake and rehabilitation for two weeks in the early postoperative period has a beneficial effect on knee extension strength in both lower limbs and BI (transfer, walking and toilet use) scores in patients with hip fracture.


Assuntos
Fraturas do Quadril/reabilitação , Força Muscular/efeitos dos fármacos , Proteínas do Soro do Leite/administração & dosagem , Idoso , Idoso de 80 Anos ou mais , Índice de Massa Corporal , Proteína C-Reativa/metabolismo , Feminino , Fraturas do Quadril/cirurgia , Humanos , Período Pós-Operatório , Treinamento de Resistência , Resultado do Tratamento , Caminhada
15.
J Chem Phys ; 141(12): 121105, 2014 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-25273405

RESUMO

To establish the fundamental understanding of the fragmentation dynamics of highly positive charged nano- and bio-materials, we carried out on-the-fly classical trajectory calculations on the fragmentation dynamics of C60(q+) (q = 20-60). We used the UB3LYP/3-21G level of density functional theory and the self-consistent charge density-functional based tight-binding theory. For q ≥ 20, we found that a two-step explosion mechanism governs the fragmentation dynamics: C60(q+) first ejects singly and multiply charged fast atomic cations C(z+) (z ≥ 1) via Coulomb explosions on a timescale of 10 fs to stabilize the remaining core cluster. Thermal evaporations of slow atomic and molecular fragments from the core cluster subsequently occur on a timescale of 100 fs to 1 ps. Increasing the charge q makes the fragments smaller. This two-step mechanism governs the fragmentation dynamics in the most likely case that the initial kinetic energy accumulated upon ionization to C60(q+) by ion impact or X-ray free electron laser is larger than 100 eV.

16.
Shokuhin Eiseigaku Zasshi ; 54(5): 370-3, 2013.
Artigo em Japonês | MEDLINE | ID: mdl-24190291

RESUMO

We observed the effect of starfish (Asterias amurensis) intake during 67 days, on rats, in terms of the activity of enzymes related to liver function and biochemical values related to weight gain, lipid metabolism and safety. 1. Starfish (Asterias amurensis) did not induce a significant difference of body weight change. 2. Starfish (Asterias amurensis) intake did not affect organ weight. 3. Starfish (Asterias amurensis) intake did not affect lipid metabolism, liver function, or protein nutrition in this experiment.


Assuntos
Ração Animal , Asterias , Saponinas/farmacologia , Ganho de Peso/efeitos dos fármacos , Animais , Asterias/química , Análise Química do Sangue , Rim/efeitos dos fármacos , Metabolismo dos Lipídeos/efeitos dos fármacos , Fígado/efeitos dos fármacos , Tamanho do Órgão/efeitos dos fármacos , Ratos , Ratos Wistar , Organismos Livres de Patógenos Específicos
17.
Clin Calcium ; 23(3): 371-6, 2013 Mar.
Artigo em Japonês | MEDLINE | ID: mdl-23445890

RESUMO

Previous studies have demonstrated close associations between QUS parameters and osteoporotic status. However, due to the ambiguities in assessing accuracy of QUS and the moderate correlation of DXA and QUS results, currently there is no agreement on how results of QUS devices should be interpreted in order to diagnose osteoporosis. However, I could recommend for clinical application that QUS should be used as the predictor of the risk of osteoporotic fractures. Good portability and low cost of QUS technique might make QUS an attractive technology for assessing risk of fractures in large populations.


Assuntos
Densidade Óssea/fisiologia , Fraturas Ósseas/diagnóstico por imagem , Osteoporose/diagnóstico , Diagnóstico por Imagem/métodos , Humanos , Medição de Risco , Ultrassonografia
18.
Genes Cells ; 18(2): 123-34, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23301696

RESUMO

Peptidoglycan (PG), also designated as murein, forms a skeletal mesh within the periplasm of bacterial membrane. PG is a metabolically stable cell architecture in Escherichia coli, but under as yet ill-defined conditions, a portion of PG is degraded, of which both amino sugar and peptide moieties are either recycled or used as self-generated nutrients for cell growth. At present, the control of PG degradation remains uncharacterized. Using the Genomic SELEX screening system, we identified an uncharacterized transcription factor YcjZ is a repressor of the expression of the initial step enzymes for PG peptide degradation. Under nutrient starvation, the genes encoding the enzymes for PG peptide degradation are derepressed so as to generate amino acids but are tightly repressed at high osmotic conditions so as to maintain the rigid membrane for withstanding the turgor. Taken together, we propose to rename YcjZ as PgrR (regulator of peptide glycan recycling).


Assuntos
Proteínas de Ligação a DNA/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Peptidoglicano/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Bases , Sítios de Ligação , Proteínas de Ligação a DNA/genética , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Genes Reporter , Motivos de Nucleotídeos , Regiões Operadoras Genéticas , Ligação Proteica , Proteólise , Fatores de Transcrição/genética , Transcrição Genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA