The effect of observation time and contrast on visual acuity

Background: Field studies of the duration of fixation during daytime driving find that it is about 0.2 seconds on average. Thus, the time available to read traffic signs is often limited. There are other circumstances where time to read alphanumeric messages is limited. Data relating time of observation are needed for purposes of ergonomic design as the data available in the literature are limited and uncertain. Method: Visual acuity was measured using Landolt rings in negative contrast, which were presented on a computer screen with a background luminance of 32 cd/m2 for durations that varied between two and 0.02 seconds at three different contrasts. Resulte: Visual acuity depends on the log of the light dose reduced by a factor that may be related to absorption of the light by the eye media. For young observers, it was found that: VA = 0.57 (log C t) + 1.705, where C is the contrast and is expressed as δL/L, where δL is the difference between target and background luminances in cd/m2 and t is the observation time in seconds. Conclusion: This formula or the functions fitted to the data obtained can be used to calculate the increase in target size needed to allow for short observation times.     

经皮椎体成形术中骨水泥填充对患者凝血功能的影响

目的:探讨经皮椎体成形术中骨水泥对骨质疏松性椎体压缩骨折患者凝血功能的影响及临床意义.方法:2006年12月至2007年12月,对24例骨质疏松性椎体压缩骨折患者行经皮椎体成形术,男6例,女18例:年龄48～83岁,平均69岁.脊柱骨折部位为T5-L3,共44个椎体,其中胸椎20个椎体,腰椎24个椎体.采用C型臂X线机透视引导下行经皮椎体成形术,注射聚甲基丙烯酸甲酯骨水泥(PMMA).分别在注入骨水泥前10min、注入骨水泥后10min、30min、1h、2h及3h时检测患者凝血功能相关指标,包括血浆凝血酶原时间(PT)、活化的部分凝血活酶时间(APTT)、凝血酶时间(TT)、纤维蛋白原(FIB)、鱼精蛋白副凝固试验(3P试验)及血浆D-二聚体(D-D)含量,并进行统计学分析.结果:经皮椎体成形术中注人骨水泥10min后PT缩短、FIB增高、3P试验阳性率升高,D-D含量增高,1h时达到高峰后开始下降.注入骨水泥后10min、30min、1h、2h四个时间点与注入骨水泥前相比较均有显著性差异(P<0.05).活化的部分凝血活酶时间(APTT)、凝血酶时间(TT)在各时间点与注入骨水泥前比较均无显著性差异(P>0.05).3h后骨水泥对这些指标的影响基本消除,各项指标与注入骨水泥前比较均无显著性差异(P>0.05).结论:经皮椎体成形术中骨水泥填充会引起患者一过性血液高凝状态,在注入骨水泥后的3h内需严密监测病情,以防血栓性疾病发生.     

Activated Protein C Reduces Graft Neutrophil Activation in Clinical Renal Transplantation

We studied the role of endogenous activated protein C (APC), the major physiological anti-coagulant with concomitant anti-inflammatory properties, on ischemia/reperfusion (I/R) in 45 patients participating in a larger trial comparing three immunosuppressive protocols in cadaveric renal transplantation: perioperative anti-thymocyte globulin (ATG, Fresenius AG, Bad Homburg, Germany), perioperative basiliximab and conventional triple therapy. Blood samples for assessing plasma APC, protein C, and lactoferrin concentrations, neutrophil CD11b and L-selectin expressions and blood leukocyte differential counts were obtained preoperatively and before reperfusion from central venous cannula, complemented with simultaneous samples from iliac artery and graft vein for calculation of transrenal differences (Delta) of study parameters at 1 and 5 min after reperfusion. Unlike basiliximab or conventional therapy groups, ATG infusion induced a substantial increase in plasma APC concentration (119 [88-144]% before infusion vs. 232 [85-1246]% after infusion, p<0.001), resulting in renal graft sequestration of APC at 1 min after reperfusion (Delta=-72 [-567 to 12]%, p<0.001). Graft APC consumption was associated with transrenal reduction of neutrophil activation markers (L-selectin r=0.7, p=0.01; lactoferrin r=-0.6, p=0.02; CD11b r=-0.8, p=0.001), and with both warm (r=0.6, p=0.01) and cold ischemia time (r=0.6, p=0.02) and donor age (r=0.6, p=0.01). These findings suggest that APC has an anti-inflammatory role in I/R injury in clinical renal transplantation.     

廊坊市农村儿童1987～1993年头胸围及交叉月龄变化的分析

本文通过对我市农村1987、1990、19933个年份中10～24月龄男女儿童头围和胸围及头胸交叉所在月龄变化的分析。表明我市农村儿童随着家庭生活水平的不断提高,其生长发育正处在长期加速阶段。同时可以看到:由于基础较差,在科学育儿方面还有较大差距,尽快克服普遍存在的落后喂养习惯和断奶食品的缺乏已成为进一步提高我市农村儿童生长发育水平的关键.应予充分重视,加以解决。     

时滞系统鲁棒稳定性的新判据

基于Ｌｙａｐｎｕｏｖ泛函方法，研究了满足匹配条件的不确定性时滞系统的鲁棒稳定性及具有稳定度β〉０鲁棒稳定性，给出了已有结果不能推出的新判据。这些新判据对已有结果难以使用的情况下也可有是有效的，或有时减少了已有结果的保守性。     

The ensemble-averaged impedance cardiogram: An evaluation of scoring methods and interrater reliability

The interrater reliability and concurrent validity of two methods of scoring the ensemble-averaged impedance cardiogram were evaluated. Impedance cardiographic and electrocardiographic signals were recorded from 40 undergraduate men and women during a baseline rest period and a vocal mental arithmetic task period. Recordings were scored by four raters using a conventional method, involving ensemble averaging after careful editing of beat-to-beat waveforms, and a streamlined method, involving ensemble averaging without beat-to-beat editing. Intraclass correlations for interrater reliability exceeded .92, whereas intraclass correlations for concurrent validity exceeded .97, indicating excellent agreement between raters and scoring methods for all cardiac measures. The streamlined method was significantly faster than the conventional method. The results indicate that variations in beat-to-beat editing do not constitute a serious source of error in the ensemble-averaged impedance cardiogram and support the interrater reliability and concurrent validity of the two scoring methods.     

End-to-side anastomosis of rat carotid artery: comparison of different types of section and shape of the terminal end

Summary In 50 rats, different types of end-to-side carotid artery anastomoses were compared. In one technique, a longitudinal split in the long axis of the vessel was performed to enhance the diameter of the anastomosis. This theoretical advantage was not confirmed in this series. The clamping time, anastomoses time, and tamponade time were increased significantly when compared with a simple, slightly oblique end-to-side anastomosis. This study highlighted that the most simple type of end-to-side anastomosis gave less bleeding, achieved a quicker water-tight anastomosis and decreased the risk of late problems.     

Effects of cocaine and quinpirole on perceptual and motor functions in baboons

 The effects of cocaine and quinpirole were studied in baboons to determine whether quinpirole, a relatively selective D₂/D₃ dopamine agonist, produced effects similar to those of cocaine on perceptual and motor processes. To measure perceptual and motor function, three baboons were trained to discriminate differences between a standard vowel and four other synthetic vowels; response accuracy as well as response latencies, or ”reaction times”, were measured following drug administrations. Cocaine reduced reaction times in two baboons, and did not affect reaction times in a third; on the other hand, quinpirole lengthened reaction times in a dose-dependent manner in all baboons. Cocaine and quinpirole also differed in the time course to produce the maximal reaction time effect following drug administration. Cocaine and quinpirole did not differ consistently in their perceptual effects, as indicated by similar changes in d′, a signal-detection index of discriminability. These distinct profiles of effects for cocaine and quinpirole suggest differing neurochemical actions for these two drugs. Received: 10 August 1996 /Final version: 16 May 1997     

Is the effect of acute hyperglycaemia on interdigestive antroduodenal motility and small-bowel transit mediated by insulin?

Acute hyperglycaemia inhibits antroduodenal motility. In non-diabetic subjects this inhibitory effect may result from reactive endogenous hyperinsulinaemia. Therefore, we investigated the effects of hyperinsulinaemia during both hyperglycaemia and euglycaemia on interdigestive antroduodenal motility (perfusion manometry) and duodenocaecal transit time (DCTT; lactulose breath-H₂ test). Six healthy volunteers (age 20–26 years) were studied for 240 min on three separate occasions in random order during: (a) i.v. saline (control); (b) acute hyperglycaemic hyperinsulinaemia (HG) with plasma glucose at 15 mmol L^?1; and (c) euglycaemic hyperinsulinaemia (HI) with plasma insulin at 80 mU L^?1 and glucose at 4–5 mmol L^?1. Results: DCTT was significantly (P < 0.05) prolonged during HG (158 ± 23 min) compared with control (95 ± 25 min), whereas HI had no effect (100 ± 17 min). Mean duration of complete migrating motor complex (MMC) cycles was significantly (P < 0.05) reduced during HG (63 ± 9 min) compared with control (103 ± 15 min) and HI (105 ± 16 min), which resulted from a significantly (P < 0.05) shorter duration of phase II. Antral motility was significantly (P < 0.05) reduced during both HI (20 ± 8 contractions 240 min^?1) and HG (9 ± 5) compared with control (43 ± 7). It is concluded that in healthy subjects hyperglycaemia prolongs DCTT, increases duodenal MMC cycle frequency and inhibits antral motility. Hyperinsulinaemia reduces antral motor activity but has no effect on interdigestive duodenal motility or DCTT. Thus, other factors, apart from insulin, mediate the inhibitory effect of hyperglycaemia on interdigestive intestinal motility and transit.     

Influence of pre-target cortical potentials on saccadic reaction times

 Saccades elicited by suddenly appearing targets show a broad distribution of reaction times. This may depend on variations in the subject’s state of preparation before target onset. To test this hypothesis, we recorded scalp event-related potentials from eight human subjects to investigate whether differences in saccadic reaction times (SRTs) are related to differences in cortical slow potentials prior to target onset. Compared with trials with medium SRTs (180–230 ms), trials with fast SRTs (130–180 ms) were found to be preceded by a more negative slow potential and trials with slow SRTs (230–280 ms) were found to be preceded by a more positive slow potential. These results support the hypothesis that cortical activation prior to target appearance influences SRTs. Received: 21 June 1996 / Accepted: 15 January 1997