Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 63
Filtrar
1.
Acta Radiol ; 64(12): 3052-3055, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-37828855

RESUMEN

BACKGROUND: Endovascular thrombectomy (EVT) is performed for acute ischemic stroke (AIS) caused by large vessel occlusion; therefore, preoperative visualization of the occluded invisible vessel course reduces complications and ensures success. Three-dimensional (3D) proton density-weighted (PDW) vessel wall imaging (VWI) using variable refocusing flip angle pulse-turbo spin-echo sequences (VRFA-TSE) with 3.0-T magnetic resonance imaging (MRI) can provide this information. PURPOSE: To assess the effectiveness of 3D PDW-VWI using 1.5-T MRI without VRFA function. MATERIAL AND METHODS: Five consecutive patients with AIS caused by large vessel occlusion underwent EVT in our institute. VWI with 1.5-T MRI using 3D PDW-fast spin echo (FSE) technique was added to conventional brain imaging. RESULTS: PDW-FSE was successfully performed in all cases. 3D PDW-FSE was useful to visualize both the anterior and posterior circulations by clearly revealing invisible vessels but could not demonstrate the length and size of the clot in all five cases. CONCLUSION: 3D PDW-FSE with 1.5-T MRI without VRFA could clearly depict the course of the invisible occluded artery and might support favorable outcomes after EVT in patients with AIS.


Asunto(s)
Accidente Cerebrovascular Isquémico , Humanos , Imagen por Resonancia Magnética/métodos , Imagenología Tridimensional/métodos , Arterias Cerebrales , Cabeza
2.
J Neuroimaging ; 32(6): 1070-1074, 2022 11.
Artículo en Inglés | MEDLINE | ID: mdl-36117145

RESUMEN

BACKGROUND AND PURPOSE: Endovascular thrombectomy (EVT) for acute ischemic stroke (AIS) caused by large vessel occlusion requires rapid and reliable imaging of the vessel course including the clot to reduce complications and ensure success. However, no method to acquire this information has been established. METHODS: Six consecutive patients with AIS caused by large vessel occlusion underwent EVT in our institute. High-resolution vessel wall MRI was performed using three-dimensional (3D) variable refocusing flip angle pulse and turbo spin-echo sequences (VRFA-TSE) with the volume isotropic turbo spin-echo acquisition (VISTA) technique. This study evaluated the effectiveness of 3D proton density-weighted (PDW) VRFA-TSE (called PDW-VISTA) compared with T2-weighted (T2W) VRFA-TSE (called T2W-VISTA) to demonstrate the cerebral vessels including the occluded invisible lesion. RESULTS: PDW-VISTA and T2W-VISTA were successfully performed in all cases. PDW-VISTA was more useful to visualize the anterior circulation than T2W-VISTA by clearly revealing invisible vessels, whereas PDW-VISTA and T2W-VISTA had similar findings in the posterior circulation. The vessel courses shown by 3D PDW-VISTA imaging before treatment and digital subtraction angiography after treatment showed good agreement in all cases. Furthermore, 3D PDW-VISTA imaging demonstrated the length and size of the clot. CONCLUSIONS: PDW-VISTA imaging was found to more clearly depict the cerebral vessels including occluded lesion than T2W-VISTA imaging. Findings of thrombus size and length were important for correctly placing the stent retriever and securing safety during the procedure.


Asunto(s)
Accidente Cerebrovascular Isquémico , Trombosis , Humanos , Imagenología Tridimensional/métodos , Imagen por Resonancia Magnética/métodos , Trombectomía
3.
Pain Ther ; 11(3): 987-1009, 2022 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-35790601

RESUMEN

INTRODUCTION: Opioid use disorder is a global problem. Although opioid analgesics are prescribed less frequently in Japan than in many other countries, the rate of aberrant prescription opioid-taking behaviors in Japan is unknown. METHODS: An internet survey was conducted to estimate the prevalence of and risk factors for prescription opioid misuse, abuse, diversion and doctor shopping in Japanese subjects with chronic pain who had been prescribed opioid analgesics. RESULTS: The proportion of respondents (n = 387) who reported opioid misuse was 45.5% (95% confidence interval [CI]: 40.4-50.6); rates were: 24.6% (95% CI: 20.3-29.2) for abuse; 15.0% (95% CI: 11.6-19.0) for diversion; and 10.6% (95% CI: 7.7-14.1) for doctor shopping. Aberrant prescription opioid-taking behaviors were higher in participants with chronic post-cancer treatment pain (misuse, 64.2%; abuse, 52.2%) or chronic cancer pain (misuse, 57.4%; abuse, 26.2%) than in those with chronic noncancer pain (misuse, 37.8%; abuse, 17.0%). Younger age, male sex, smoking, habitual drinking, diagnosis of psychiatric disease, use of opioids other than tramadol, and use of opioids for chronic post-cancer treatment pain and chronic cancer pain were identified as risk factors for aberrant prescription opioid-taking behaviors. CONCLUSION: Even in Japan, which has not experienced the surge in opioid consumption documented in other countries, aberrant prescription opioid-taking behaviors were observed. When prescribing opioid analgesics, universal precautions should always be taken for both cancer and non-cancer patients. TRIAL REGISTRATION: UMIN000041788.

4.
Biomed Microdevices ; 23(1): 3, 2021 01 06.
Artículo en Inglés | MEDLINE | ID: mdl-33404966

RESUMEN

Cell-assisted lipotransfer (CAL) is an advanced lipoinjection method that uses autologous lipotransfer with addition of a stromal vascular fraction (SVF) containing adipose-derived stromal stem cells (ASCs). The CAL procedure of manual isolation of cells from fat requires cell processing to be performed in clean environment. To isolate cells from fat without the need for a cell processing center, such as in a procedure in an operation theater, we developed a novel method for processing SVF using a closed cell washing concentration device (CCD) with a hollow fiber membrane module. The CCD consists of a sterilized closed circuit, bags and hollow fiber, semi-automatic device and the device allows removal of >99.97% of collagenase from SVF while maintaining sterility. The number of nucleated cells, ASCs and viability in SVF processed by this method were equivalent to those in SVF processed using conventional manual isolation. Our results suggest that the CCD system is as reliable as manual isolation and may also be useful for CAL. This approach will help in the development of regenerative medicine at clinics without a cell processing center.


Asunto(s)
Tejido Adiposo , Células del Estroma , Recuento de Células , Medicina Regenerativa , Células Madre
5.
Neuropsychiatr Dis Treat ; 16: 3063-3070, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33335397

RESUMEN

PURPOSE: The objective of this post hoc analysis was to explore the relationship, including changes over time, between baseline clinical symptom characteristics and working ability, judged by investigators, after 12 weeks of antidepressant monotherapy in Japanese patients with major depressive disorder (MDD) and painful physical symptoms (PPS) in a real-world clinical setting. PATIENTS AND METHODS: This prospective, observational study in patients treated with duloxetine or selective serotonin reuptake inhibitors was conducted from 2014 to 2016. Both treatment groups were pooled and divided into 2 groups, "working ability recovered" or "working ability not recovered," based on working ability at the end of the study. Patients were also divided into 4 subgroups by the presence or absence of previous depressive episodes and working ability. Main outcome measures included baseline demographics and clinical characteristics, and the 17-item Hamilton Rating Scale for Depression (HAM-D17). RESULTS: Comparison between "working ability recovered" (n=122) and "working ability not recovered" (n=91) showed that the percentage of patients with complications and psychotherapy at baseline, and baseline HAM-D17 total, insomnia, somatic, and anxiety scores, were significantly different. The results of subgroup analyses were mostly the same as the results analyzed by working ability alone. Although statistical differences were observed for some outcome measures, the differences at baseline, except use of psychotherapy, may not be applicable clinically, and there were no specific trends observed that could predict working ability. CONCLUSION: This post hoc analysis suggested that most baseline clinical characteristics, including the presence or absence of previous depressive episodes, were not predictive of working ability recovery. However, the use of psychotherapy in parallel with antidepressant monotherapy may be positively associated with working ability recovery. All outcome measures improved over time, reinforcing the importance of continuous treatment and observation to improve and accurately judge working ability in patients with MDD and PPS.

6.
J Diabetes Investig ; 11(2): 450-457, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-31314173

RESUMEN

AIMS/INTRODUCTION: To assess the prevalence of diabetic polyneuropathy (DPN)-related sensory symptoms/signs and associated factors in patients with polyneuropathy, considering non-linear effects for numerical variables. MATERIALS AND METHODS: A cross-sectional survey of patients with type 2 diabetes mellitus from 17 primary care clinics across Japan was carried out. DPN and DPN-related sensory symptoms/signs were diagnosed according to the Diabetic Neuropathy Study Group in Japan criteria. RESULTS: Of the 9,914 patients with type 2 diabetes mellitus in this study, 2,745 had DPN and 1,689 had DPN-related sensory symptoms/signs (61.5% of patients with DPN). There were significant correlations between DPN-related sensory symptoms/signs and smoking status (odds ratio 2.04 for current and 1.64 for former; P < 0.001 and P = 0.002, respectively), sex (odds ratio 0.56 for male/female; P < 0.001) and alcohol consumption (odds ratio 2.02 for former/never; P = 0.004). Based on the non-linear logistic regression model, significant correlations were observed between the presence of DPN-related sensory symptoms/signs and higher systolic blood pressure (SBP), longer diabetes duration, and decreasing age. The logarithm of odds for SBP increased until reaching approximately 130 mmHg, then it plateaued. CONCLUSIONS: Some modifiable factors assessed in the large survey database might be associated with DPN-related sensory symptoms/signs, namely smoking, alcohol consumption and SBP. Maintaining SBP <130 mmHg was associated with lower odds of DPN-related sensory symptoms/signs in patients with DPN.


Asunto(s)
Diabetes Mellitus Tipo 2/epidemiología , Neuropatías Diabéticas/epidemiología , Anciano , Estudios Transversales , Femenino , Humanos , Japón , Masculino , Persona de Mediana Edad , Dinámicas no Lineales
7.
Neuropsychiatr Dis Treat ; 15: 809-817, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31040680

RESUMEN

OBJECTIVE: To investigate the relationship between Hamilton Depression Rating Scale (HAM-D) score and psychiatrists' judgment of working ability in patients with major depressive disorder (MDD) and painful physical symptoms. METHODS: This was a prospective, observational, 12-week study in patients who received duloxetine or a selective serotonin reuptake inhibitor. Patients were ≥20 years old, resided in Japan, and had at least moderate depression (Quick Inventory of Depressive Symptomatology ≥16) and at least moderate painful physical symptoms (Brief Pain Inventory-Short Form average pain ≥3). The main outcome in this post-hoc analysis was the HAM-D17 cutoff best corresponding with patients' working ability according to the investigator's judgment. Area under the receiver-operator curve was used to determine the time point with the strongest relationship between HAM-D17 and working ability. The optimal HAM-D17 cutoff was determined based on the maximum of sensitivity (true positive rate) minus ([1 minus specificity] [true negative rate]). For the evaluation of binary data, a mixed effects model with repeated measures analysis was used. RESULTS: For the estimation of the HAM-D17 cutoff, the area under the receiver-operator curve was maximal at 12 weeks, when a HAM-D17 score of 6 resulted in the best correspondence with working ability in the combined study population. At 12 weeks, a HAM-D17 score of 6 also resulted in the maximum predictive ability in each of the two treatment groups separately. For predicted working ability at 12 weeks, 52.7% of duloxetine-treated patients achieved the HAM-D17 cutoff of ≤6, whereas 48.5% of SSRIs-treated patients achieved HAM-D17 ≤6 (P=0.477). CONCLUSION: In this study of patients with major depressive disorder and painful physical symptoms, a HAM-D17 score ≤6 corresponded best with patients' working ability. This finding is consistent with previous studies showing that a HAM-D17 cutoff of ≤7 may overestimate functional recovery from MDD.

8.
Neuropsychiatr Dis Treat ; 13: 2115-2124, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-28831260

RESUMEN

OBJECTIVE: To examine how clinical and demographic patient baseline characteristics influence effectiveness of duloxetine versus selective serotonin reuptake inhibitor (SSRI) treatment, in real-world Japanese clinical settings of patients with major depressive disorder (MDD) and associated painful physical symptoms (PPS). METHODS: This was a multicenter, 12-week, prospective, observational study in patients with MDD (Quick Inventory of Depressive Symptomatology ≥16) and at least moderate PPS (Brief Pain Inventory-Short Form [BPI-SF] average pain ≥3). Patients received duloxetine or SSRIs (escitalopram, sertraline, paroxetine, or fluvoxamine). Assessments were made by using BPI-SF average pain, 17-item Hamilton Rating Scale for Depression (HAM-D17), EuroQol 5-dimension questionnaire, Social Adaptation Self-Evaluation Scale, Global Assessment of Functioning, and ability to work. Predefined subgroups included the number of previous episodes of depression (0 vs ≥1), baseline BPI-SF average pain score (≤6 vs >6), baseline HAM-D17 total score (≤18 vs >18), baseline HAM-D17 retardation (≤7 vs >7) and anxiety somatic subscale scores (≤6 vs >6), and age (<65 vs ≥65 years). RESULTS: Treatment effectiveness was evaluated in 523 patients (duloxetine N=273, SSRIs N=250). Treatment with duloxetine was superior to SSRIs on most outcome measures in patients experiencing their first depressive episode, those with higher baseline PPS levels, and in patients with more severe baseline depression. This was also the case for older patients. In patients with less severe depression, SSRI treatment tended to show more improvements in depression and quality of life measures versus duloxetine treatment. CONCLUSION: These preplanned subgroup analyses of data from a prospective observational study suggest that, for Japanese MDD patients with PPS, duloxetine is more effective than SSRIs in patients with a first episode of MDD, with more severe depression, or more severe PPS.

9.
Neuropsychiatr Dis Treat ; 13: 2105-2114, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-28831259

RESUMEN

OBJECTIVE: The objective of this study was to assess the effectiveness of duloxetine monotherapy, in comparison with selective serotonin reuptake inhibitor (SSRI) monotherapy, in the treatment of painful physical symptoms (PPS) in Japanese patients with major depressive disorder (MDD) in real-world clinical settings. METHODS: This was a multicenter, 12-week prospective, observational study. This study enrolled MDD patients with at least moderate PPS, defined as a Brief Pain Inventory-Short Form (BPI-SF) average pain score (item 5) ≥3. Patients were treated with duloxetine or SSRIs (escitalopram, sertraline, paroxetine, or fluvoxamine) for 12 weeks, and PPS were assessed by BPI-SF average pain score. The primary outcome was early improvement in the BPI-SF average pain score at 4 weeks post-baseline. RESULTS: A total of 523 patients were evaluated for treatment effectiveness (duloxetine N=273, SSRIs N=250). The difference in BPI-SF average pain score between the two groups was not statistically significant at 4 weeks post-baseline, the primary endpoint (least-squares mean change from baseline [95% confidence interval]: duloxetine, -2.8 [-3.1, -2.6]; SSRIs, -2.5 [-2.8, -2.3]; P=0.166). There was a numerical advantage for duloxetine in improvement from 4 to 12 weeks post-baseline, and the difference was statistically significant at 8 weeks post-baseline (least-squares mean change from baseline [95% confidence interval]: duloxetine, -3.6 [-3.9, -3.3]; SSRIs, -3.1 [-3.4, -2.8]; P=0.023). The 30% and 50% responder rates were significantly higher in patients treated with duloxetine at 4 and 8 weeks post-baseline. There were no serious adverse events experienced by duloxetine-treated patients. The rate of discontinuations due to adverse events was similar for duloxetine and the SSRIs (1.0% and 0.8% of patients, respectively). CONCLUSION: In this observational study, BPI-SF improvement was not significantly different at 4 weeks, the primary endpoint; however, patients treated with duloxetine tended to show better improvement in PPS compared to those treated with SSRIs.

10.
Opt Express ; 24(18): 20080-8, 2016 Sep 05.
Artículo en Inglés | MEDLINE | ID: mdl-27607617

RESUMEN

We provide an overview of Fano resonance and plasmon induced transparency (PIT) as well as on plasmons coupling in planar structures, and we discuss their application in sensing and enhanced spectroscopy. Metal-insulator-metal (MIM) structures, which are known to support symmetric and anti-symmetric surface plasmon polaritons (SPPs) arising from the coupling between two SPPs at the metal-insulator interfaces, exhibit anticrossing behavior of the dispersion relations arising from the coupling of the symmetric SPP and the metal/air SPP. Multilayer structures, formed by a metal film and a high-index dielectric waveguide (WG), separated by a low-index dielectric spacer layer, give narrow resonances of PIT and Fano line shapes. An optimized Fano structure shows a giant field intensity enhancement value of 106 in air at the surface of the high-index dielectric WG. The calculated field enhancement factor and the figure of merit for the sensitivity of the Fano structure in air can be 104 times as large as those of the conventional surface plasmon resonance and WG sensors.

11.
Nihon Koshu Eisei Zasshi ; 63(12): 750-757, 2016.
Artículo en Japonés | MEDLINE | ID: mdl-28100894

RESUMEN

Objectives We launched and engaged in the "Ajinadai Lively Project" to examine the ideal state of community building in an urban semi-marginal village. In addition to discussing its progress and describing the activities, we examine future challenges.Methods (1) We gathered existing resources, conducted a district survey and focus group interview, and investigated the community's health issues. (2) We conducted a workshop with local residents and formulated an action plan. (3) We conducted a health volunteer training class to foster community leaders. (4) Local residents interacted with students through nursing school practice and student volunteer activities.Results The health issues in the community were as follows: (1) Few connections existed between residents across generations, and no framework for mutual assistance was established. (2) Many solitary elderly people and elderly households existed, and we found many instances of elderly-to-elderly care and social withdrawal of elderly people. (3) Many slopes and staircases existed, which made mobility difficult for elderly people. Based on these results, we encouraged the state to pursue quality of life as "A community where people connect and help one another across generations" as well as "A healthy community where people greet one another." We also established health, behavioral, and environmental goals. The health volunteer training class became an impetus for residents to realize the necessity of not only protecting their own health, but also encouraging others and the whole community to get involved.Conclusion While the health volunteer training class did not initiate autonomous activity, it increased the motivation of residents themselves for community building. Performing continuous evaluations and offering support for autonomous activity is important in the future.


Asunto(s)
Calidad de Vida , Participación de la Comunidad , Humanos , Encuestas y Cuestionarios , Población Urbana
12.
Appl Opt ; 54(15): 4889-94, 2015 May 20.
Artículo en Inglés | MEDLINE | ID: mdl-26192528

RESUMEN

A guided-mode (GM) sensor with a dielectric waveguide grating formed on a thin reflective film using Kretschmann configuration is proposed. Numerical results based on a finite-element method approach indicate a significant resolution improvement due to the excitation of a GM supported by the waveguide grating-sensing media system. The applicability of the waveguide theory to the design of waveguide gratings is validated by a comparison to the exact electromagnetic theory. Strong localization of an electromagnetic field in the sensing media within the grating with intensity enhancement up to two orders of magnitude is demonstrated. The sensor has potential for biological sensing and imaging applications.

13.
Opt Lett ; 38(23): 5067-70, 2013 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-24281511

RESUMEN

A terahertz (THz) wire-grid polarizer is fabricated by imprinting porous Si followed by oblique evaporation of Ag. We demonstrate that it works in a wide frequency region covering from 5 to 18 THz with the extinction ratio of 10 dB. The frequency region is much wider than that of THz wire-grid polarizers fabricated by conventional imprint lithography using organic materials. The result suggests that imprinting of porous Si is a promising fabrication technique to realize low-cost wire-grid polarizers working in the THz region.

14.
Opt Express ; 21(9): 10651-8, 2013 May 06.
Artículo en Inglés | MEDLINE | ID: mdl-23669921

RESUMEN

The radiative decay rate of a dipole emitter inside the core of a multi-layered dielectric sphere is theoretically investigated. It is shown that, when the thickness of each layer coincides with a quarter wavelength, the multi-layered sphere has a great potential to work as a three-dimensional photonic crystal with a high quality factor and a small mode volume. From the analysis of the dipole position dependence of a radiative decay rate, we show that a smaller core radius, a quarter wavelength at the smallest, is more suitable for real applications. The investigation on the tolerance for thickness nonuniformity reveals that the thickness variation of 10% is tolerable.


Asunto(s)
Materiales Manufacturados/análisis , Modelos Químicos , Resonancia por Plasmón de Superficie/instrumentación , Simulación por Computador , Diseño Asistido por Computadora , Conductividad Eléctrica , Diseño de Equipo , Análisis de Falla de Equipo , Estudios de Factibilidad , Fotones
15.
In Vivo ; 27(3): 333-7, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-23606688

RESUMEN

BACKGROUND: In neonate mice exposed to diethylstilbestrol (neoDES), vaginal epithelium shows persistent proliferation and stratification even after ovariectomy. Tissue recombination studies suggest that neonatally-estrogenized vaginal stroma can induce vaginal epithelial hyperplasia depending on the stromal age. This study examined the proliferative effect of the vaginal stroma from 8-day-old mice treated with DES on the vaginal epithelia of 8-day-old and adult mice. MATERIALS AND METHODS: Vaginal epithelium and stroma from 8-day-old and adult mice was recombined, and grafted to ovariectomized host mice. RESULTS: The 5-bromo-2'-deoxyuridine (BrdU)-labeled cells in the epithelium and the number of epithelial cell layers were not significantly different between epithelia from 8-day-old and adult mice when combined with stroma from 8-day-old control mice. BrdU-labeled cells in the vaginal epithelia from both age groups combined with the stroma from 8-day-old neoDES mice exhibited higher values. The epithelium from neoDES adult mice had a lower percentage of BrdU-labeled cells. CONCLUSION: The stroma from 8-day-old neoDES mice induces epithelial cell proliferation, but lower stromal cell proliferation.


Asunto(s)
Carcinógenos/farmacología , Comunicación Celular/efectos de los fármacos , Dietilestilbestrol/farmacología , Células Epiteliales/metabolismo , Células del Estroma/metabolismo , Vagina/citología , Vagina/efectos de los fármacos , Animales , Animales Recién Nacidos , Bromodesoxiuridina/metabolismo , Proliferación Celular/efectos de los fármacos , Femenino , Ratones
16.
Analyst ; 138(4): 995-9, 2013 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-23304700

RESUMEN

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS) using GaP nanoparticles (NPs) prepared by a gas evaporation method was investigated on poly(ethylene glycol)s (PEGs). The mass spectra of PEG and survival yield measurements suggested that larger GaP NPs have a quite high soft ionization ability.

17.
Opt Lett ; 37(11): 1877-9, 2012 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-22660059

RESUMEN

Nonlinear optical responses of boron (B)-doped silicon nanocrystals (Si-ncs) embedded in borosilicate glass were studied by z-scan and optical Kerr gate methods under femtosecond excitation at 780 nm. The nonlinear refractive index (n(2)) and the two photon absorption coefficients (ß) of B-doped Si-ncs were found to be 3 times enhanced, compared to those of intrinsic Si-ncs. The response time was faster than 100 fs even at 5 K. The origin of the large nonlinear optical response was discussed, based on the experimental data of n(2), electron spin resonance spectra, and linear absorption spectra.

18.
Opt Lett ; 36(21): 4221-3, 2011 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-22048371

RESUMEN

Developing Si compatible optical sources has attracted a great deal of attention owing to the potential for forming inexpensive, monolithic Si-based integrated devices. In this Letter, we show that ultra broadband near-IR (NIR) luminescence in the optical telecommunication window of silica optical fibers was obtained for Bi-doped silicon-rich silica films prepared by a co-sputtering method. Without excess Si, i.e., Bi-doped pure silica films, no luminescence was observed in the NIR range. A broad Bi-related NIR photoluminescence appears when excess Si was doped in the Bi-doped silica. The luminescence properties depended strongly on the amount of excess Si and the annealing temperature. Photoluminescence results suggest that excess Si acts as an agent to activate Bi NIR luminescence centers and also as an energy donor to transfer excitation energy to the centers. It is believed that this peculiar structure might find some important applications in Si photonics.

19.
Opt Lett ; 36(20): 4026-8, 2011 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-22002374

RESUMEN

Si nanocrystals (Si-NCs) dispersible in polar liquid without surface functionalization by organic molecules have been realized by simultaneously doping n and p type impurities. We show that the codoped Si-NCs are stable in methanol for more than five months, while intrinsic Si-NCs prepared by the same procedure form large agglomerates. The different behavior of the intrinsic and codoped Si-NCs in solutions suggests that doped impurities exist on the surface of Si-NCs and the surface potential is large enough to prevent the agglomeration. The colloidal solution of codoped Si-NCs exhibits broad photoluminescence with the maximum in the near infrared range (1.1-1.3 eV).

20.
Opt Lett ; 36(19): 3951-3, 2011 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-21964152

RESUMEN

Porous Si made from (110) Si wafers exhibits strong in-plane optical anisotropy (birefringence) in the visible and near-IR ranges. Oxidation of the birefringent porous Si results in the formation of birefringent porous silica. We demonstrate that the degree of the birefringence of porous silica can be controlled by the oxidation condition, and very small birefringence can be achieved. The smallest anisotropy of the refractive index (Δn) is 0.001, which is about ten times smaller than that of quartz. The small birefringence allows us to produce true zero-order wave plates operating in the UV range.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...