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1.
J Prev Alzheimers Dis ; 9(4): 752-757, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36281680

RESUMO

BACKGROUND: There is growing interest in examining objective markers for early identification and behavioral intervention to prevent dementia and mild cognitive impairment in clinical and community settings. OBJECTIVE: To investigate the association between salivary alpha-amylase as an objective measure of psychological stress response and mild cognitive impairment for the implication of psychological stress in the development of mild cognitive impairment. DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional study involved 865 participants aged ≥ 65 years. A saliva sample was collected in the morning, and the levels of salivary alpha-amylase were assayed. Mild cognitive impairment was evaluated using the Japanese version of the Montreal Cognitive Assessment; a score < 26 was indicative of mild cognitive impairment. A multivariable logistic regression model was used to examine the association of salivary alpha-amylase and mild cognitive impairment after adjusting for age, sex, current drinking status, current smoking status, body mass index, hypertension, diabetes mellitus, physical activity, education, social support, social network, and heart rate variability. RESULTS: Salivary alpha-amylase was associated with mild cognitive impairment (the multivariable-adjusted odds ratio [95% confidence interval] for the 1-standard deviation increment of log-transformed salivary alpha-amylase was 1.24 [1.07-1.44]). This significant association persisted after adjusting for various confounding factors. CONCLUSION: Elevation of salivary alpha-amylase was associated with mild cognitive impairment among Japanese community-dwelling older adults. This suggests that salivary alpha-amylase is a useful objective marker of psychological stress responses associated with mild cognitive impairment.


Assuntos
Disfunção Cognitiva , alfa-Amilases Salivares , Humanos , Idoso , Estudos Transversais , Japão , Testes de Estado Mental e Demência , Biomarcadores
2.
Rev Sci Instrum ; 90(8): 083002, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31472606

RESUMO

We developed a laser system for the spectroscopy of the clock transition in ytterbium (Yb) atoms at 578 nm based on an interference-filter stabilized external-cavity diode laser (IFDL) emitting at 1156 nm. Owing to the improved frequency-to-current response of the laser-diode chip and the less sensitivity of the IFDL to mechanical perturbations, we succeeded in stabilizing the frequency to a high-finesse ultra-low-expansion glass cavity with a simple current feedback system. Using this laser system, we performed high-resolution clock spectroscopy of Yb and found that the linewidth of the stabilized laser was less than 320 Hz.

3.
Benef Microbes ; 7(4): 501-9, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27013460

RESUMO

We previously reported that dietary heat-killed Lactobacillus brevis SBC8803 affects sleep rhythms in mice. The present study evaluated the effect of consumption of heat-killed SBC8803 on sleep architecture in humans. A non-randomised, placebo-controlled, double blind, and crossover pilot study was conducted using volunteers who scored at a slightly high level (i.e. ≥6) on the Athens Insomnia Scale (AIS). Male subjects (n=17; age 41-69 y) consumed placebo or SBC8803 capsules (25 mg/day of heat-killed SBC8803) for 10 days. Electroencephalograms (EEG) were recorded using a mobile, one-channel system, providing objective data on sleep. Subjects' sleep journals and administration of the AIS provided subjective data on sleep. Three subjects were excluded from the statistical analysis. Analysis of the remaining 14 volunteers revealed no significant differences between placebo and SBC8803 consumption in either the AIS or the sleep EEG. The sleep journals revealed an improvement in 'waking' for the SBC8803 consumption periods (P=0.047), and there was a marginally significant effect on 'drowsiness during the following day' (P=0.067). Effects on the EEG delta power value (µV(2)/min) were revealed by a stratified analysis based on age, AIS, and the Beck Depression Inventory (BDI). Specifically, effects were found among subjects in their 40s who consumed the SBC8803 capsules (P=0.049) and among subjects with a BDI score less than the all-subjects average (13.3) (P=0.045). A marginally significant effect was found among subjects with an AIS score less than the all-subjects average (11.6) (P=0.065). The delta power value of 5 subjects with both BDI and AIS scores less than the average increased significantly (P=0.017). While the number of subjects was limited, a beneficial effect on sleep due to consumption of heat-killed L. brevis SBC8803 was found in subjects with slightly challenged sleep.


Assuntos
Levilactobacillus brevis , Transtornos do Sono-Vigília/dietoterapia , Sono , Adolescente , Adulto , Idoso , Estudos Cross-Over , Dieta , Método Duplo-Cego , Eletroencefalografia , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Adulto Jovem
4.
J Laryngol Otol ; 129(8): 812-6, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26119908

RESUMO

BACKGROUND: Infratemporal fossa abscess following odontogenic infection is not rare, and usually occurs as a sequela of dental disease. Infratemporal fossa abscess was previously treated with the combination of buccal incision and temporal incision, or via a transoral approach. METHOD: This paper reports a case of infratemporal fossa abscess in a 51-year-old female. RESULTS: The abscess was drained transnasally via an endoscopic modified medial maxillectomy approach, preserving the inferior turbinate and nasolacrimal duct. The pain remitted the next day and trismus had diminished in one week. CONCLUSION: The transnasal approach with endoscopic modified medial maxillectomy is a direct, minimally invasive method that provides a direct field of view for drainage of infratemporal fossa abscess. This approach is recommended for infratemporal fossa abscess.


Assuntos
Abscesso/diagnóstico , Abscesso/cirurgia , Endoscopia/métodos , Maxila/patologia , Maxila/cirurgia , Sinusite Maxilar/diagnóstico , Sinusite Maxilar/cirurgia , Procedimentos Cirúrgicos Minimamente Invasivos/métodos , Músculos Pterigoides/patologia , Músculos Pterigoides/cirurgia , Cirurgia Assistida por Computador/métodos , Drenagem/métodos , Feminino , Humanos , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X
5.
Nutr Metab Cardiovasc Dis ; 25(7): 651-8, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26026210

RESUMO

BACKGROUND: We examined associations between fish and n-3 LCFA and mortality in a prospective study with a large proportion of blacks with low socio-economic status. METHODS AND RESULTS: We observed 6914 deaths among 77,604 participants with dietary data (follow-up time 5.5 years). Of these, 77,100 participants had available time-to-event data. We investigated associations between mortality with fish and n-3 LCFA intake, adjusting for age, race, sex, kcal/day, body mass index (BMI), smoking, alcohol consumption, physical activity, income, education, chronic disease, insurance coverage, and meat intake. Intakes of fried fish, baked/grilled fish and total fish, but not tuna, were associated with lower mortality among all participants. Analysis of trends in overall mortality by quintiles of intake showed that intakes of fried fish, baked/grilled fish and total fish, but not tuna, were associated with lower risk of total mortality among all participants. When participants with chronic disease were excluded, the observed association remained only between intakes of baked/grilled fish, while fried fish was associated with lower risk of mortality in participants with prevalent chronic disease. The association between n-3 LCFA intake and lower risk of mortality was significant among those with diabetes at baseline. There was an inverse association of mortality with fried fish intake in men, but not women. Total fish and baked/grilled fish intakes were associated with lower mortality among blacks while fried fish intake was associated with lower mortality among whites. Effect modifications were not statistically significant. CONCLUSION: Our findings suggest a modest benefit of fish consumption on mortality.


Assuntos
Dieta , Ácidos Graxos Ômega-3 , Peixes , Mortalidade , Pobreza/estatística & dados numéricos , Fatores Etários , Animais , População Negra , Estudos de Coortes , Culinária , Diabetes Mellitus/epidemiologia , Inquéritos sobre Dietas , Etnicidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Risco , Fatores Sexuais , Fatores Socioeconômicos , Estados Unidos/epidemiologia , População Branca
6.
Phys Rev Lett ; 115(25): 256405, 2015 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-26722935

RESUMO

We study the electronic structure of bulk single crystals and epitaxial films of Fe_{3}O_{4}. Fe 2p core level spectra show clear differences between hard x-ray (HAX) and soft x-ray photoemission spectroscopy (PES). The bulk-sensitive spectra exhibit temperature (T) dependence across the Verwey transition, which is missing in the surface-sensitive spectra. By using an extended impurity Anderson full-multiplet model-and in contrast to an earlier peak assignment-we show that the two distinct Fe species (A and B site) and the charge modulation at the B site are responsible for the newly found double peaks in the main peak above T_{V} and its T-dependent evolution. The Fe 2p HAXPES spectra show a clear magnetic circular dichroism (MCD) in the metallic phase of magnetized 100-nm-thick films. The model calculations also reproduce the MCD and identify the contributions from magnetically distinct A and B sites. Valence band HAXPES shows a finite density of states at E_{F} for the polaronic half metal with a remnant order above T_{V} and a clear gap formation below T_{V}. The results indicate that the Verwey transition is driven by changes in the strongly correlated and magnetically active B-site electronic states, consistent with resistivity and optical spectra.

7.
Phys Rev Lett ; 111(21): 217001, 2013 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-24313517

RESUMO

We performed temperature dependent x-ray linear dichroism (XLD) experiments on an iron pnictide system, Ba(Fe(1-x)Co(x))2As2 with x=0.00, 0.05, 0.08, and 0.10 to experimentally verify the existence of orbital ordering (OO). Substantial XLD was observed in polarization dependent x-ray absorption spectra of Fe L edges. By exploiting the difference in the temperature dependent behaviors, OO, and structure contributions to XLD could be clearly separated. The observed OO signal indicates different occupation numbers for d(yz) and d(zx) orbitals and supports the existence of ferro-OO. The results are also consistent with the theoretical prediction. Moreover, we find substantial OO signal well above the structural and magnetic transition temperatures, which suggests the existence of strong OO fluctuations up to high temperatures.

8.
J Laryngol Otol ; 127(7): 716-20, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23750668

RESUMO

OBJECTIVE: To describe a case of giant cell reparative granuloma of the temporal bone which extended into the middle-ear cavity, and which was successfully treated surgically via a transmastoid approach, with hearing preservation. CASE: A 37-year-old man presented with a one-year history of right-sided hearing loss, complicated by a three-month history of otalgia and a sensation of aural fullness. Computed tomography and magnetic resonance imaging demonstrated an osteolytic tumour lesion in the right temporal bone. The diagnosis was confirmed by biopsy from the mastoid lesion. INVESTIGATION AND INTERVENTION: Pure-tone audiometry, computed tomography and magnetic resonance imaging were conducted, followed by total resection. RESULT: The giant cell reparative granuloma of the temporal bone was completely resected, with preservation of hearing. CONCLUSION: Although this patient's giant cell reparative granuloma of the temporal bone extended into the middle-ear cavity, total resection was achieved, with preservation of hearing. To the best of our knowledge, hearing preservation following resection of giant cell reparative granuloma of the temporal bone has not previously been reported.


Assuntos
Granuloma de Células Gigantes/cirurgia , Perda Auditiva Unilateral/etiologia , Neoplasias Cranianas/cirurgia , Adulto , Audiometria de Tons Puros , Orelha Média/diagnóstico por imagem , Orelha Média/patologia , Granuloma de Células Gigantes/complicações , Granuloma de Células Gigantes/diagnóstico , Perda Auditiva Unilateral/prevenção & controle , Humanos , Imageamento por Ressonância Magnética , Masculino , Neoplasias Cranianas/complicações , Neoplasias Cranianas/diagnóstico , Osso Temporal/diagnóstico por imagem , Osso Temporal/patologia , Osso Temporal/cirurgia , Tomografia Computadorizada por Raios X , Resultado do Tratamento
9.
Eur J Neurol ; 19(6): 905-10, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22288427

RESUMO

BACKGROUND AND PURPOSE: Shortened telomere length has been considered to be associated with various age-related diseases, especially in dementia such as Alzheimer's disease and vascular dementia. However, changes in telomere length in dementia with Lewy bodies (DLB) remain unclear. To elucidate these changes, we set out to determine telomere length in peripheral leukocytes as well as the level of urinary 8-hydroxy-deoxyguanosine (8-OHdG) as a marker of oxidative stress in DLB. METHODS: Blood samples were obtained from 33 patients with a clinical diagnosis of probable DLB and 35 age-matched, non-demented elderly controls (NEC). Telomere length was assessed by quantitative real-time polymerase chain reaction of genomic DNA extracted from leukocytes, whereas oxidative stress was assessed on the basis of urine 8-OHdG level, which was measured using high-performance liquid chromatography. RESULTS: Telomere length was significantly shorter in the DLB group than in the NEC group. Urinary 8-OHdG levels were significantly higher in the DLB group than in the NEC group. There was a negative correlation between telomere length and age in the DLB group; however, there were no significant relationships between telomere length and clinical findings including disease duration, severity of cognitive decline, presence or absence of fluctuation in cognitive function, visual hallucinations, and Parkinsonism. In both groups, the correlation between telomere length and urinary 8-OHdG levels was not significant. CONCLUSIONS: These findings indicate that the etiopathology of DLB is considered to be an accelerated aging process.


Assuntos
Corpos de Lewy/ultraestrutura , Doença por Corpos de Lewy/patologia , Telômero/patologia , 8-Hidroxi-2'-Desoxiguanosina , Idoso , Idoso de 80 Anos ou mais , Desoxiguanosina/análogos & derivados , Desoxiguanosina/urina , Feminino , Humanos , Corpos de Lewy/patologia , Doença por Corpos de Lewy/urina , Masculino , Índice de Gravidade de Doença , Estatística como Assunto
10.
Int J Oral Maxillofac Surg ; 40(6): 584-92, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21371862

RESUMO

The aim of this study was to examine the effects of mandibular setback surgery on pharyngeal airway space and respiratory function during sleep. The subjects were 22 patients in whom mandibular prognathism was corrected by bilateral sagittal split ramus osteotomy; either one jaw or two jaw surgery. Polysomnography was performed before surgery and 6 months after surgery, and the apnea hypopnea index (AHI) and arterial oxygen saturation during sleep were measured to assess respiratory function during sleep. Morphological changes were studied using cephalograms taken immediately before, a few days after and 6 months after surgery. As a control, 10 subjects without sleep-disordered breathing underwent the same examinations. AHI was not changed significantly after surgery, although two patients were diagnosed with mild obstructive sleep apnea (OSA) syndrome after surgery. They were not obese, but the amounts of mandibular setback at surgery were large. In conclusion, a large amount of mandibular setback might inhibit biological adaption and cause sleep-disordered breathing, and it might be better to consider maxillary advance or another technique that does not reduce the airway for patients with skeletal class III malocclusions who have large anteroposterior discrepancy and/or maxillary hypoplasia.


Assuntos
Mandíbula/cirurgia , Orofaringe/patologia , Procedimentos Cirúrgicos Ortognáticos/métodos , Prognatismo/cirurgia , Respiração , Sono/fisiologia , Adaptação Fisiológica/fisiologia , Adolescente , Adulto , Cefalometria/métodos , Assimetria Facial/cirurgia , Feminino , Seguimentos , Humanos , Masculino , Má Oclusão Classe III de Angle/cirurgia , Mandíbula/patologia , Maxila/patologia , Maxila/cirurgia , Nasofaringe/patologia , Mordida Aberta/cirurgia , Procedimentos Cirúrgicos Ortognáticos/instrumentação , Osteotomia/instrumentação , Osteotomia/métodos , Osteotomia de Le Fort/instrumentação , Osteotomia de Le Fort/métodos , Oxigênio/sangue , Polissonografia/métodos , Complicações Pós-Operatórias , Sela Túrcica/patologia , Síndromes da Apneia do Sono/classificação , Apneia Obstrutiva do Sono/etiologia , Adulto Jovem
11.
Phys Rev Lett ; 106(4): 047602, 2011 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-21405362

RESUMO

We study the surface and bulk electronic structure of the room-temperature ferromagnet Co∶TiO(2) anatase films using soft- and hard-x-ray photoemission spectroscopy with probe sensitivities of ∼1 and ∼10 nm, respectively. We obtain direct evidence of metallic Ti(3+) states in the bulk, which get suppressed to give a surface semiconductor, thus indicating the difference in electronic structure between surface and bulk. X-ray absorption and resonant photoemission spectroscopy reveal Ti(3+) electrons at the Fermi level (E(F)) and high-spin Co(2+) electrons occurring away from E(F). The results show the importance of the charge neutrality condition: Co(2+)+V(O)(2-)+2Ti(4+)↔Co(2+)+2Ti(3+) (V(O) is oxygen vacancy), which gives rise to the elusive Ti 3d carriers mediating ferromagnetism via the Co 3d-O 2p-Ti 3d exchange interaction pathway of the occupied orbitals.

12.
Acta Neurol Scand ; 124(2): 104-8, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20849398

RESUMO

OBJECTIVE: To clarify the clinical manifestations of adult-onset Alexander disease (AOAD) in Japanese patients with glial fibrillary acidic protein (GFAP) gene mutations. METHODS AND MATERIALS: Twelve patients of AOAD with GFAP mutations detected in our centre were examined for neurological and magnetic resonance imaging (MRI) findings. RESULTS: Major symptoms were pyramidal and bulbar signs. In addition, three patients presented abnormal behaviour and/or memory disturbance. Two of the three patients also had Parkinsonism and had been diagnosed with fronto-temporal dementia or progressive supranuclear palsy until GFAP mutations were detected. Abnormalities of the medulla oblongata and cervical spinal cord were observed on MRI in all patients. CONCLUSIONS: Patients presenting with pyramidal and/or bulbar signs with abnormalities of the medulla oblongata and cervical spinal cord on MRI should be considered for GFAP analysis as this is the typical presentation of AOAD. Abnormal behaviour and cognitive disorders including deterioration of memory were rare symptoms but could be an obstacle to diagnosing Alexander disease.


Assuntos
Doença de Alexander/genética , Proteína Glial Fibrilar Ácida/genética , Mutação/genética , Adulto , Idade de Início , Idoso , Doença de Alexander/diagnóstico , Tronco Encefálico/patologia , Análise Mutacional de DNA , Feminino , Humanos , Japão , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Exame Neurológico/métodos , Medula Espinal/patologia
13.
Phys Rev Lett ; 104(23): 236404, 2010 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-20867257

RESUMO

We investigate the electronic structure of chromium nitride (CrN) across the first-order magnetostructural transition at T(N)∼286 K. Resonant photoemission spectroscopy (PES) shows a gap in the 3d partial density of states at the Fermi level and an on-site Coulomb energy U∼4.5 eV, indicating strong electron-electron correlations. Bulk-sensitive high-resolution (6 meV) laser PES reveals a clear Fermi edge indicating an antiferromagnetic metal below T(N). Hard x-ray Cr 2p core-level PES shows T-dependent changes across T(N) which originate from screening due to coherent states as substantiated by cluster model calculations using the experimentally observed U. Electrical resistivity confirms an insulator above T(N) (E(g)∼70 meV) becoming a disordered metal below T(N). Thus, CrN transforms from a correlated insulator to an antiferromagnetic metal, coupled to the magnetostructural transition.

14.
Phys Rev Lett ; 104(24): 247201, 2010 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-20867330

RESUMO

Electronic structures of the quantum critical superconductor ß-YbAlB4 and its polymorph α-YbAlB4 are investigated by using bulk-sensitive hard x-ray photoemission spectroscopy. From the Yb 3d core level spectra, the values of the Yb valence are estimated to be ∼2.73 and ∼2.75 for α- and ß-YbAlB4, respectively, thus providing clear evidence for valence fluctuations. The valence band spectra of these compounds also show Yb2+ peaks at the Fermi level. These observations establish an unambiguous case of a strong mixed valence at quantum criticality for the first time among heavy fermion systems, calling for a novel scheme for a quantum critical model beyond the conventional Doniach picture in ß-YbAlB4.

15.
Phys Rev Lett ; 104(10): 106401, 2010 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-20366439

RESUMO

The Magnéli phase Ti(4)O(7) exhibits two sharp jumps in resistivity with coupled structural transitions as a function of temperature at T(c1) approximately 142 K and T(c2) = 154 K. We have studied electronic structure changes across the two transitions using 7 eV laser, soft x-ray, and hard x-ray (HX) photoemission spectroscopy (PES). Ti 2p-3d resonant PES and HX PES show a clear metallic Fermi edge and mixed valency above T(c2). The low temperature phase below T(c1) shows a clear insulating gap of approximately 100 meV. The intermediate phase between T(c1) and T(c2) indicates a pseudogap coexisting with remnant coherent states. HX PES and complementary calculations have confirmed the coherent screening in the strongly correlated intermediate phase. The results suggest the existence of a highly anomalous state sandwiched between the mixed-valent Fermi liquid and charge ordered Mott-insulating phase in Ti(4)O(7).

16.
Phys Rev Lett ; 104(6): 066407, 2010 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-20366842

RESUMO

Epitaxial ultrathin Fe films on fcc Cu(001) exhibit a spin spiral (SS), in contrast to the ferromagnetism of bulk bcc Fe. We study the in-plane (IP) and out-of-plane (OP) Fermi surfaces (FSs) of the SS in 8 monolayer Fe/Cu(001) films using energy-dependent soft-x-ray momentum-resolved photoemission spectroscopy. We show that the SS originates in nested regions confined to OP FSs, which are drastically modified compared to IP FSs. From precise reciprocal-space maps in successive zones, we obtain the associated real space compressive strain of 1.5+/-0.5% along c axis. An autocorrelation analysis quantifies the incommensurate ordering vector q=(2pi/a)(0,0, approximately 0.86), favoring a SS and consistent with magneto-optic Kerr effect experiments. The results reveal the importance of IP and OP FS mapping for ultrathin films.

17.
J Oral Rehabil ; 36(11): 808-13, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19744262

RESUMO

Although the number of sound or decayed teeth has been reported to be associated with cognitive function in elderly populations with dementia, little is known about this association in elderly populations without dementia. We evaluated this relationship, with adjustment for confounding factors, in Japanese populations of 60-year-old (n = 270; 120 males and 150 females) and 65-year-old (n = 123; 57 males and 66 females) individuals residing in Fukuoka Prefecture of Japan. Dental examinations were performed in all subjects, along with the Mini-mental state examination (MMSE) for assessing cognitive function. Among the total of 393 subjects, the mean MMSE score was 27.9 +/- 1.9, and 391 subjects scored 24 or higher. The mean numbers of sound and decayed teeth were 12.0 +/- 6.3 and 0.5 +/- 1.2, respectively. Associations were found between the numbers of sound and decayed teeth and MMSE in total subjects and males, but not in females, by multiple regression analysis adjusted for gender, age, level of education, marital status, smoking, alcohol drinking, working status, systolic blood pressure and blood glucose. An association was also found between MMSE and the number of sound teeth in a logistic regression analysis. In conclusion, associations were found between normal-range cognitive function and the numbers of sound and decayed teeth, after adjustment for various confounding factors, in an elderly Japanese population.


Assuntos
Transtornos Cognitivos/epidemiologia , Cárie Dentária/epidemiologia , Higiene Bucal/normas , Doenças Periodontais/epidemiologia , Autocuidado/normas , Idoso , Pressão Sanguínea/fisiologia , Transtornos Cognitivos/complicações , Inquéritos de Saúde Bucal , Feminino , Indicadores Básicos de Saúde , Humanos , Japão/epidemiologia , Masculino , Pessoa de Meia-Idade , Doenças Periodontais/etiologia , Características de Residência
18.
Phys Rev Lett ; 102(23): 236401, 2009 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-19658952

RESUMO

We have studied the valence redistribution of V in LaAlO(3)/LaVO(3)/LaAlO(3) trilayers, which are composed of only polar layers grown on SrTiO3 (001) substrates, by core-level photoemission spectroscopy. We have found that the V valence is intermediate between V3+ and V4+ for thin LaAlO3 cap layers, decreases with increasing cap-layer thickness, and finally recovers the bulk value of V3+ at approximately 10 unit-cell thickness. In order to interpret these results, we propose that the atomic reconstruction of the polar LaAlO3 surface competes with the purely electronic V valence change so that the polar catastrophe is avoided at the cost of minimum energy.

19.
Rev Sci Instrum ; 80(2): 023905, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19256660

RESUMO

We have developed an ultrahigh-vacuum instrument for resonant diffraction experiments using polarized soft x rays in the energy range of hnu=300-2000 eV at beamline BL17SU of SPring-8. The diffractometer consists of modified differentially pumped rotary feedthroughs for theta-2theta stages, a sample manipulator with motor-controlled x-y-z-, tilt (chi)-, and azimuth (phi)-axes, and a liquid helium flow-type cryostat for temperature dependent measurements between 30 and 300 K. Test results indicate that the diffractometer exhibits high reproducibility (better than 0.001 degrees ) for a Bragg reflection of alpha-quartz 100 at a photon energy of hnu=1950 eV. Typical off- and on-resonance Bragg reflections in the energy range of 530-1950 eV could be measured using the apparatus. The results show that x-ray diffraction experiments with energy-, azimuth-, and incident photon polarization-dependence can be reliably measured using soft x rays in the energy range of approximately 300-2000 eV. The facility can be used for resonant diffraction experiments across the L-edge of transition metals, M-edge of lanthanides, and up to the Si K-edge of materials.

20.
Phys Rev Lett ; 101(13): 137601, 2008 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-18851493

RESUMO

High energy resolution photoelectron spectroscopy of conduction electrons in the vicinity of the Fermi edge in Al and Au at excitation energies of 880 and 7940 eV was carried out using synchrotron radiation. For the excitation energy of 7940 eV, the observed Fermi energy of Al shows a remarkable shift to higher binding energy as compared with that of Au, with accompanying broadening. This is due to the recoil effect of the emitted photoelectrons. The observed spectra are well reproduced by a simple model of Bloch electrons based on the isotropic Debye model.

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