Geometry-invariant gradient refractive index lens: analytical ray tracing

A new class of gradient refractive index (GRIN) lens is introduced and analyzed. The interior iso-indicial contours mimic the external shape of the lens, which leads to an invariant geometry of the GRIN structure. The lens model employs a conventional surface representation using a coincoid of revolution with a higher-order aspheric term. This model has a unique feature, namely, it allows analytical paraxial ray tracing. The height and the angle of an arbitrary incident ray can be found inside the lens in a closed-form expression, which is used to calculate the main optical characteristics of the lens, including the optical power and third-order monochromatic aberration coefficients. Moreover, due to strong coupling of the external surface shape to the GRIN structure, the proposed GRIN lens is well suited for studying accommodation mechanism in the eye. To show the power of the model, several examples are given emphasizing the usefulness of the analytical solution. The presented geometry-invariant GRIN lens can be used for modeling and reconstructing the crystalline lens of the human eye and other types of eyes featuring a GRIN lens.     

Validating self-reported strokes in a longitudinal UK cohort study (Whitehall II): Extracting information from hospital medical records versus the Hospital Episode Statistics database

Background

Quantiles are a staple of epidemiologic research: in contemporary epidemiologic practice, continuous variables are typically categorized into tertiles, quartiles and quintiles as a means to illustrate the relationship between a continuous exposure and a binary outcome.

Discussion

In this paper we argue that this approach is highly problematic and present several potential alternatives. We also discuss the perceived drawbacks of these newer statistical methods and the possible reasons for their slow adoption by epidemiologists.

Summary

The use of quantiles is often inadequate for epidemiologic research with continuous variables.     

左腋动脉和臂丛神经走行变异1例

笔者在标本解剖操作观察腋窝结构时发现1例左侧腋动脉与臂丛神经位置及走行出现变异,既往文献报道的变异多为腋动脉发出的分支与臂丛神经之间的位置与走行之间变异^[1-3],本次解剖观察发现腋动脉与臂丛神经的内侧束、外侧束和后束之间的位置关系出现变异,与既往报道有所不同,现报告如下。     

Electrospinning of polyhydroxyalkanoate fibrous scaffolds: effects on electrospinning parameters on structure and properties

In this study, electrospinning was used to prepare ultrafine fibers from PHAs with different chemical compositions: P(3HB) and copolymers: P(3HB-co-4HB), P(3HB-co-3HV), and P(3HB-co-3HHx). The main process parameters that influence ultrafine fiber diameter and properties (polymer concentration, solution feeding rate, working distance, and applied voltage) have been investigated and their effects evaluated. The study revealed electrospinning parameters for the production of high-quality ultrafine fibers and determined which parameters should be varied to tailor the properties of the products. This study is the first to compare biological and physical-mechanical parameters of PHAs with different chemical compositions as dependent upon the fractions of monomers constituting the polymers and ultrafine fiber orientation. Mechanical strength of aligned ultrafine fibers prepared from different PHAs is higher than that of randomly oriented ones; no significant effect of ultrafine fiber orientation on surface properties has been found. None of the fibrous scaffolds produced by electrospinning from PHAs had any adverse effects on attachment, growth, and viability of NIH 3T3 mouse fibroblast cells, and all of them were found to be suitable for tissue engineering applications.     

VEGF-C表达和微淋巴管密度与胃癌淋巴转移的关系及意义

目的探讨胃癌组织血管内皮生长因子C(VEGF-C)表达和微淋巴管密度(MLVD)及两者与胃癌淋巴转移的关系。方法应用免疫组织化学方法检测208例人胃癌组织、40例癌浸润前缘组织及139例人胃正常粘膜组织中VEGF-C、D2-40的表达,对D2-40阳性脉管进行MLVD计数,并结合病理资料进行统计学分析。结果胃癌组织VEGF-C的表达明显高于正常胃粘膜组织(χ2=109.199,P<0.01);胃癌组织中有淋巴结转移(χ2=14.496,P<0.01)或浸润透浆膜(χ2=11.586,P<0.01)组VEGF-C表达水平分别较无转移或浸润未及浆膜组增高。癌浸润前缘组织中MLVD(18.36±15.60个/mm2)明显高于胃癌组(9.41±9.32个/mm2,t=-3.681,P<0.01)和胃正常粘膜组织(7.70±7.69个/mm2,t=-4.180,P<0.01);胃癌淋巴结转移组MLVD(9.81±9.97个/mm2)高于无转移组(6.41±7.85个/mm2,t=2.516,P<0.01),而在浸润透浆膜组(11.20±10.55个/mm2)和未及浆膜组(8.54±9.36个/mm2)MLVD无差别(t=1.467,P=0.472)。另外,在胃癌组织中VEGF-C表达与MLVD呈正相关(F=2.910,P<0.05)。结论VEGF-C在胃癌中的高表达与胃癌浸润深度、淋巴转移密切相关。     

Ammonium Salts Promote Functional Adaptation of Rat Erythrocytes on the Model of Forced Swimming

Bulletin of Experimental Biology and Medicine - Ammonium, an end-product of catabolism, in low doses can promote adaptation of metabolic pathways in erythrocytes under conditions of extreme...     

Reciprocal effect of Waardenburg syndrome mutations on DNA binding by the Pax-3 paired domain and homeodomain

The Pax-3 protein contains two DNA-binding domains, a paired domain and a homeodomain. Mutations in Pax-3 cause Waardenburg syndrome (WS) in humans and the mouse Splotch (Sp) phenotype. In the Sp-delayed mouse, a mutation in the Pax-3 paired domain (G9R) abrogates the DNA-binding activity of both the paired domain and the homeodomain, suggesting that they may functionally interact. To investigate this possibility further, we have analyzed the DNA-binding properties of additional point mutants in the Pax-3 paired domain and homeodomain that occur in WS patients (F12L, N14H, G15S, P17L, R23L, G48A, S51F and G66D in the paired domain, V47F and R53G in the homeodomain), the Pax-1 un mutation (G15A) and a substitution associated with Peters' anomaly in the PAX-6 gene (R23G). Within the paired domain, seven of 10 mutations were found to abrogate DNA-binding by the paired domain. Remarkably, these seven mutations also affected DNA binding by the homeodomain, causing either a complete loss (P17L and G66D), a reduction (R23G, R23L, G15S and G15A) or an increase in DNA-binding activity (N14H). In addition, the effect of paired domain mutations occurred at the level of monomer formation by the homeodomain, while the dimerization potential of this domain seemed unaffected in mutants where it could be analyzed. Furthermore, while both homeodomain mutations were found to abolish DNA binding by this domain, the R53G mutation also abrogated DNA binding by the paired domain. The important observation that independent mutations in either domain can affect DNA binding by the other in the intact Pax- 3 protein strongly suggests that the two domains are not functionally independent but bind DNA through cooperative interactions. Modeling the deleterlous mutations on the three-dimensional structure of the paired domain of Drosophila Prd shows that these mutations cluster at the DNA interface, thus suggesting that a series of DNA contacts are essential for DNA binding by both the paired domain and the homeodomain of Pax-3.      

1140919448CD200-dependent suppression of human NK activity by IVIG requires CD200 receptor type 2

Problem: IVIG prepared from plasma of stored human blood can be efficacious in improving pregnancy success in a selected subgroup of patients but RCTs using an IVIG showing inferior suppression of NK activity in vitro have been negative (J Assist Reprod Genet 2006). A significant component of NK suppression by IVIG appears to be due to CD200 released into plasma from PBL during storage at 4C. CD200 receptors (CD200R) are expressed at the fetomaternal interface prior to onset of abortion; CD200R1 mediates direct effects on gamma‐delta T cell development and suppresses alpha‐beta T cell responses in vitro, whereas CD200R2 alters DC so as to facilitate development of alpha‐beta Treg cells. Which receptor(s) mediate NK cell suppression? Methods: Purified human PBL or the CD56⁺ NK cell subset of PBL were used to lyse 51Cr‐labeled K562 cells in vitro. Different IVIG preparations were tested for suppressive ability, and suppression was blocked by either anti‐huCD200 mAb or rabbit anti‐huCD200R1 or R2 antibodies. Results: CD200‐dependent IVIG NK suppressive potency differed among IVIG types (Gammagard>Gamunex>>Gamimmune). CD200‐dependent suppression was blocked by anti‐CD200R antibody able to react with the type 2 receptor. K562 cells did not express receptor, and purified CD56⁺ NK cells were suppressed effectively without the need for non‐NK cells. Conclusions: IVIG may directly express NK cell activity via CD200 binding to CD200R2.