Separate detectors for simple and complex grating patterns?

Grating having two sinusoidal components show a periodic variation in contrast which is visible as a "beat" pattern. The spatial frequency of the beat is the difference between the frequencies of the two components. Thresholds for a number of detection and discrimination tasks were measured using beat patterns of 1 c/deg (with components of 9 and 10 c/deg), and gratings of 1 and 10 c/deg. Temporal modulation at 6 Hz lowered detection thresholds for 1 c/deg gratings, but not for beats or 10 c/deg gratings. The effect of contrast on the range of temporal frequencies over which direction of movement can be discriminated differs for the three types of pattern: beats resemble neither low nor high spatial frequency gratings. Low and (for 2 of 3 observers) high spatial frequency gratings, but not beat patterns, are susceptible to a movement after effect induced by a low spatial-frequency grating. Beat patterns induce little or no movement after effect. We conclude that beat patterns are not detected by the same mechanisms that detect simple gratings.     

49例造影剂副反应及急救体会

讨论了影像造影剂使用过程中副反应的发生率、发生原因、急救方法和预防措施。     

顽固性复发性气胸胸膜腔造影及硬化治疗后追踪

对32例顽固性复发性气胸患者用60%泛影葡胺进行胸膜腔造影,确定裂口后作硬化剂治疗,并作复张后胸部CT对照及手术追踪对照,取得满意效果。     

瞬间反应式二次谐波显像评价正常犬肝脏超声学造影的实验研究

目的：评价瞬间反应二次谐波显像（Ｔｒａｎｓｉｅｎｔ ｒｅｓｐｏｎｓｅ ｓｅｃｏｎｄ ｈａｒｍｏｎｅｃ ｉｍａｇｉｎｇ,ＴＲＳＨＩ）对正常肝脏声学造影的增强效果及动态变化规律,并与常规连续二次谐波显像进行对比分析。方法：６只健康杂种犬 经外周静脉注射氟碳声学造影剂,分别用常规二次谐波显像和瞬间反应式二次谐波显像扫描肝脏。造影效果评价使用视觉评分和视频密度分析。结果：常规二次谐波显像有４次Ｉ级增强、４     

Study of the Complex Between the Contrast Agent lobitridol (Xenetix®) and Elastase (PPE): A Model for Hydrophobic Site Protection in Drug-Protein Interactions

Purpose. The concept of Hydrophilic Sphere Stabilization, or Hydrophobic Shielding, has been postulated in the synthesis of biocompatible contrast agents in vascular imaging. To improve the safety of these polyiodinated agents, interactions with protein hydrophobic sites in biomacromolecules should be kept as low as possible. In order to evaluate the level of interactions with proteins, we have selected the serine proteinase Elastase, in presence of Iobitridol (Xenetix^®), as a model. Methods. The complex between Iobitridol and Pancreatic Porcine Elastase was investigated by X-ray diffraction techniques, on saturated monocrystals, using the synchrotron radiation at 0.98. Results. In contrast to Iohexol, which displays several interactions including one in the active site, Iobitridol is unable to interact directly with elastase. Only one partially occupied site is found in between two molecules of the crystal packing. Conclusions. The validation of the 'hydrophobic shielding' concept, which was at the origin of the design of the Iobitridol molecule, has been proven to be an essential feature in minimizing in vivo protein interactions.     

Towards an ethics of immediacy A defense of a noncontractual foundation of the care giver—patient relationship

In this article, I argue that the relationship between patients and their health care providers need not be construed as a contract between moral strangers. Contrary to the (American) legal presumption that health care providers are not obligated to assist others in need unless the latter are already contracted patients of record, I submit that the presence of a suffering human being constitutes an immediate moral commandment to try to relieve such suffering. This thesis is developed in reference to the French philosopher Levinas and the Dutch theologian Schillebeeckx. An expanded version of the biblical parable of the Good Samaritan serves as test case.This revised version was published online in October 2005 with corrections to the Cover Date.     

中国健康中青年女性全血比粘度参考值与海拔高度的关系

目的：为制定中国健康中青年女性全血比粘度参考值的统一标准提供科学依据。方法：收集了中国各地用毛细管法测定的健康中青年女性全血比粘度参考值,并对其与海拔高度的关系进行了研究。结果：发现随着海拔高度的逐渐增大,健康中青年女性全血比粘度参考值也在逐渐增大,相关性很显著。用一元回归分析的方法推导出一个回归方程。结论：如果知道了中国某地的海拔高度,就可以用回归方程估算这个地区的健康中青年女性全血比粘度参考值。     

Cardiac effects of contrast media in MR angiography: evaluation in an experimental model of myocardial ischemia

RATIONALE AND OBJECTIVES: The authors evaluated the cardiac tolerability of paramagnetic contrast agents for magnetic resonance (MR) angiography in an in vitro model of ischemic rat heart. MATERIALS AND METHODS: The left anterior descending coronary artery was temporarily occluded in a perfused rat heart model to induce cardiac ischemia and reperfusion. A dose of 0.4 mL of gadobenate dimeglumine, of gadopentetate dimeglumine, or of D-mannitol was injected directly into the aorta both during the ischemia and during the reperfusion period. The left ventricular pressure and heart rate were recorded. RESULTS: Myocardial ischemia resulted in decreased cardiac activity, with a reduction in left ventricular pressure and heart rate. A further decrease in cardiac activity was temporarily induced by injection of contrast medium during both the ischemic and early reperfusion phases. Less marked responses were induced by a hyperosmolal solution of mannitol. CONCLUSION: These results suggest that the transient cardiac effects induced by bolus injection of paramagnetic contrast medium may be regarded as the combined effects of the osmotoxicity of the contrast medium solution and the chemotoxicity of the contrast medium molecule.     

A multiscale spatial filtering account of the White effect, simultaneous brightness contrast and grating induction

Blakeslee and McCourt ((1997) Vision Research, 37, 2849-2869) demonstrated that a multiscale array of two-dimensional difference-of-Gaussian (DOG) filters provided a simple but powerful model for explaining a number of seemingly complex features of grating induction (GI), while simultaneously encompassing salient features of brightness induction in simultaneous brightness contrast (SBC), brightness assimilation and Hermann Grid stimuli. The DOG model (and isotropic contrast models in general) cannot, however, account for another important group of brightness effects which includes the White effect (White (1979) Perception, 8, 413-416) and the demonstrations of Todorovic ((1997) Perception, 26, 379-395). This paper introduces an oriented DOG (ODOG) model which differs from the DOG model in that the filters are anisotropic and their outputs are pooled nonlinearly. The ODOG model qualitatively predicts the appearance of the test patches in the White effect, the Todorovic demonstration, GI and SBC, while quantitatively predicting the relative magnitudes of these brightness effects as measured psychophysically using brightness matching. The model also accounts for both the smooth transition in test patch brightness seen in the White effect (White & White (1985) Vision Research, 25, 1331-1335) when the relative phase of the test patch is varied relative to the inducing grating, and for the spatial variation of brightness across the test patch as measured using point-by-point brightness matching. Finally, the model predicts intensive aspects of brightness induction measured in a series of Todorovic stimuli as the arms of the test crosses are lengthened (Pessoa, Baratoff, Neumann & Todorokov (1998) Investigative Ophthalmology and Visual Science, Supplement, 39, S159), but fails in one condition. Although it is concluded that higher-level perceptual grouping factors may play a role in determining brightness in this instance, in general the psychophysical results and ODOG modeling argue strongly that the induced brightness phenomena of SBC, GI, the White effect and the Todorovic demonstration, primarily reflect early-stage cortical filtering operations in the visual system.