983 resultados para 809.812


Relevância:

60.00% 60.00%

Publicador:

Resumo:

光学元件的破坏是限制高功率激光系统发展的主要问题,理解光学元件的破坏机制对于高功率激光系统的设计、运行参量选择以及器件技术发展有重要影响。以热辐射模型为基础研究了杂质吸收诱导光学薄膜破坏的热力过程。研究发现薄膜发生初始破坏所需时间很短,脉冲的大部分时间是引起薄膜发生更大的破坏。在考虑吸收杂质发生相变的情况下,计算了吸收杂质汽化对薄膜产生的蒸汽压力,论证了薄膜发生宏观破坏的可能性。此模型能很好地解释光学薄膜的平底坑破坏形貌。

Relevância:

60.00% 60.00%

Publicador:

Resumo:

The 808nm laser diodes with a broad waveguide are designed and fabricated. The thickness of the Al_(0.35)-Ga_(0.65)As waveguide is increased to 0.9μm. In order to suppress the super modes, the thickness of the Al_(0.55)Ga_(0.45)As cladding layers is reduced to only 0.7μm while keeping the transverse radiation losses of the fundamental mode below 0.2cm~(-1). The structures are grown by metal organic chemical vapour deposition. The devices show excellent performances. The maximum output power of 10.2W in the 100μm broad-area laser diodes is obtained.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

 电子冷却系统中冷却力的大小与电子束的温度密切相关。由于强流电子束自身产生的空间电荷场,使得电子束的速度离散,增加了电子束温度,降低了冷却效率。为了减小空间电荷效应,HIRFL CSR的电子冷却系统将首次采用空心电子束对储存环中的重离子束流进行冷却。通过分析实心电子束和空心电子束的空间电荷场,研究了其对电子束速度和温度的影响。

Relevância:

60.00% 60.00%

Publicador:

Resumo:

A multi-phase model was developed and Tb(III) speciation in human blood plasma was studied. At a concentration below 3.744x 10(-4) mol/L (or at the concentration), Tb(III) is mostly bound to phosphate to form precipitate of TbPO4. As the concentration of Tb(III) increases, phosphate is exceeded and another kind of precipitate of Tb-2(CO3)(3) appears. Among soluble Tb(III) species, Tb(III) mainly distribute in [Tb (Tf)] at low concentration and in [Tb (HSAA, [Tb-2 (Tf)], [Th (IgG)], [Tb (Lactate)](2+), [Tb (CitArgH)] and free Tb(III) at high concentration.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

LnCl(3) reacted with C6H5CH2C5H4Na in THF (tetrahydrofuran) in the ratio 1.1 at room temperature for 1 h giving C(6)H(5)CH(2)C(6)H(4)LnCl(2) . nTHF, which reacted with C8H8K2/THF and the crystals obtained were recrystallized in DME to yield the title complex. The crystal structure of (C8H8) Ln (C6H5CH2C5H4). DME was determined revealing that the Gd complex has one conformation. One benzylcyclopentadienyl (eta(5)), one cyclooctatetraenyl (eta(8)) and the two oxygen atoms of DME (dimethoxyethane) are coordinated to Gd with the effective coordination number of 10.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Self-organization(1,2) occurs in plasmas when energy progressively transfers from smaller to larger scales in an inverse cascade(3). Global structures that emerge from turbulent plasmas can be found in the laboratory(4) and in astrophysical settings; for example, the cosmic magnetic field(5,6,) collisionless shocks in supernova remnants(7) and the internal structures of newly formed stars known as Herbig-Haro objects(8). Here we show that large, stable electromagnetic field structures can also arise within counter-streaming supersonic plasmas in the laboratory. These surprising structures, formed by a yet unexplained mechanism, are predominantly oriented transverse to the primary flow direction, extend for much larger distances than the intrinsic plasma spatial scales and persist for much longer than the plasma kinetic timescales. Our results challenge existing models of counter-streaming plasmas and can be used to better understand large-scale and long-time plasma self-organization.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Pollen is routinely monitored, but it is unknown whether pollen counts represent allergen exposure. We therefore simultaneously determined olive pollen and Ole e 1 in ambient air in C"ordoba, Spain, and "Evora, Portugal, using Hirst-type traps for pollen and high-volume cascade impactors for allergen. Pollen from different days released 12-fold different amounts of Ole e 1 per pollen (both locations P < 0.001). Average allergen release from pollen (pollen potency) was much higher in C"ordoba (3.9 pg Ole e 1/pollen) than in "Evora (0.8 pg Ole e 1/pollen, P = 0.004). Indeed, yearly olive pollen counts in C"ordoba were 2.4 times higher than in "Evora, but Ole e 1 concentrations were 7.6 times higher. When modeling the origin of the pollen, >40% of Ole e 1 exposure in "Evora was explained by high-potency pollen originating from the south of Spain. Thus, olive pollen can vary substantially in allergen release, even though they are morphologically identical.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

BackgroundThe pathogenesis of melasma and the role of keratinocytes in disease development and maintenance are not completely understood. Dermal abnormalities, the expression of inflammatory mediators, growth factors, epithelial expression of melanocortin and sexual hormones receptors suggest that not only melanocytes, but entire epidermal melanin unit is involved in melasma physiopathology.ObjectivesTo compare nuclear morphological features and chromatin texture between basal keratinocytes in facial melasma and adjacent normal skin.MethodsWe took facial skin biopsies (2mm melasma and adjacent normal skin) from women processed for haematoxylin and eosin. Thirty non-overlapping basal keratinocyte nuclei were segmented and descriptors of area, highest diameter, perimeter, circularity, pixel intensity, profilometric index (Ra) and fractal dimension were extracted using ImageJ software.ResultsBasal keratinocyte nuclei from facial melasma epidermis displayed larger size, irregular shape, hyperpigmentation and chromatin heterogeneity by fractal dimension than perilesional skin.ConclusionBasal keratinocytes from facial melasma display changes in nuclear form and chromatin texture, suggesting that the phenotype differences between melasma and adjacent facial skin can result from complete epidermal melanin unit alterations, not just hypertrophic melanocytes.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Background: Recent evidence suggests an association between migraine and bipolar disorder (BD), although the impact of this association in the clinical course of BD is relatively unknown. Objective: This study aimed to compare 2 groups of individuals with BD (with vs without comorbid migraine) and evaluate differences in severity of clinical course. Methods: Three hundred thirty-nine adults with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition defined bipolar or II disorder were enrolled and divided into 2 groups: with and without comorbid migraine. Demographic and clinical data were obtained using standardized interviews. Results: Patients with comorbid migraines had more mood episodes, especially those with depressive polarity. In addition, comorbid migraine was associated with a higher prevalence of psychiatric and general medical comorbidities. Differences between the 2 groups in number of lifetime hospitalizations for depression/mania, rates of rapid cycling, and history of suicide attempts were not observed after Bonferroni correction. Conclusions: Comorbid migraine seems to be associated with poor outcomes in BD. Additional studies should be conducted to investigate shared vulnerabilities and pathophysiologic mechanisms as well as treatment optimization of both illnesses. (C) 2012 Elsevier Inc. All rights reserved.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

We present a 5.3-Myr stack (the ''LR04'' stack) of benthic d18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm. This is the first benthic delta18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene. We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the delta18O stack to a simple ice model based on 21 June insolation at 65 N. Stacked sedimentation rates provide additional age model constraints to prevent overtuning. Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 5.3 Myr and in the precession band for more than half of the record. The LR04 stack contains significantly more variance in benthic delta18O than previously published stacks of the late Pleistocene as the result of higher resolution records, a better alignment technique, and a greater percentage of records from the Atlantic. Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of delta18O from 2.7-1.6 Ma is primarily a deep-water temperature signal and that the phase of d18O precession response changed suddenly at 1.6 Ma.