亮度知觉效应与视觉加工方式研究

目的:利用微持续与微间隔时间技术,设计了两组相关的实验,对亮度知觉效应和视觉加工方式进行探讨。方法:实验于2006-06在中南民族大学物理楼脑认知实验室进行,所有受试者为年龄20～25岁的大学本科生,视力(含矫正视力)正常,均为右利手。①实验1:被试为10名(男5名,女5名),要求被试分别对n屏依次呈现的亮块的明度和n 1屏依次呈现的亮块的明度进行比较(n≤17)。②实验2:被试为28名(男13名,女15名),实验涉及两个刺激物,先呈现的刺激物由左右两个大小相同、亮度不同的亮块a和b组成,后呈现的刺激物把a和b的位置进行对调,当这两个刺激物依次显示时,要求被试报告左右两边的明度是否存在差异,存在何种差异。结果:①实验1∶1≤n≤3时,100%的被试报告,n 1屏的明度大于n屏的亮度,即n 1>n;4≤n≤10时,70%～90%的被试报告n 1>n;n>10时,50%～70%的被试报告n 1>n;随着n值的增加明度差异也在减小,大约在n=17时达到稳定,n屏和n 1屏的明度区别将很难被看出。②实验2:在L(a)b a,随着a和b的亮度差异减小,左右两边呈现的明度越相似;同样当L(a)相似文献   

High prevalence of hepatitis B virus pre-s mutant in countries where it is endemic and its relationship with genotype and chronicity

It has been reported that hepatitis B virus (HBV) mutants carrying mutations in the pre-S region can be found in infected patients. In this study, we investigated the prevalence of the HBV variant with the pre-S mutant in different geographic regions, including countries with low and high levels of endemic HBV infection, and analyzed the correlation with clinical findings. We examined 387 HBV DNA-positive serum samples from individuals among 12 countries, consisting of Vietnam, Myanmar, Thailand, China, Korea, Nepal, Japan, Russia, Spain, United States, Bolivia, and Ghana. HBV pre-S mutants were detected in 71 (18.3%) of 387 serum samples tested. This mutant was the most prevalent in Vietnam (36%), followed by Nepal (27.3%), Myanmar (23.3%), China (22.4%), Korea (14.3%), Thailand (10.5%), Japan (7.7%), and Ghana (4.3%). In contrast, no case with this mutation was found in Russia, Spain, United States, and Bolivia. Among the HBV deletion mutations, 15.5% (11 of 71) occurred in the pre-S1 and 46.5% (33 of 71) in the pre-S2 regions. Eight (11.3%) cases had a mutation in both the pre-S1 and pre-S2 regions. In addition, a point mutation at the pre-S2 starting codon was observed in 19 (26.7%) cases. The detection rate of the HBV mutant in patients with hepatocellular carcinoma was significantly higher than in other patients (P < 0.05). Furthermore, these mutants were found more frequently in genotype B (25%) and genotype C (24.5%) than in the other genotypes (P < 0.05). Our results indicated that there was a high prevalence of HBV pre-S mutation in regions of endemic HBV infection in Asia. Furthermore, the pre-S mutation appeared to be correlated with hepatocellular carcinoma and HBV genotypes.     

Endobronchial foreign bodies in Vietnamese adults are related to eating habits

Background and objective: A high percentage of bronchoscopically extracted foreign bodies in Ho Chi Minh City were pits of the sapote fruit, a finding previously unreported. This paper presents a review of foreign body extractions, which identifies the substances found, documents the diagnostic pathway and draws attention to the specific aspiration risk of the sapote pit. Methods: The records of 100 consecutive adults who were found to have a bronchial foreign body during flexible bronchoscopy were reviewed. Results: In 83% of patients, the foreign body extraction was performed more than 2 weeks after the aspiration had occurred. In only 34% of patients was the diagnosis of an aspirated foreign body considered early in the patient's clinical course. The most frequent foreign bodies found were sapote pits (41%), followed by small bones (38%). Foreign bodies were lodged more frequently in the right bronchial tree (64%). In 98% of patients, the foreign bodies were successfully removed with the flexible scope. There was one postoperative death, which was not ascribed to the procedure. Conclusions: Physicians need to consider foreign body aspirations when evaluating patients with recurrent pneumonia, unexplained cough or atelectasis. Awareness of this problem might lead to public health measures that could reduce the incidence of these aspirations.     

Detection and characterization of diarrheagenic Escherichia coli from young children in Hanoi, Vietnam

Diarrhea continues to be one of the most common causes of morbidity and mortality among infants and children in developing countries. Escherichia coli is an emerging agent among pathogens that cause diarrhea. The development of a highly applicable technique for the detection of different categories of diarrheagenic E. coli is important. We have used multiplex PCR by combining eight primer pairs specific for enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli, enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC). This facilitates the identification of five different categories of diarrheagenic E. coli from stool samples in a single reaction simultaneously. The prevalences of diarrheagenic E. coli were 22.5 and 12% in the diarrhea group and the control group, respectively. Among 587 fecal samples from Vietnamese children under 5 years of age with diarrhea, this technique identified 132 diarrheagenic E. coli strains. This included 68 samples (11.6%) with EAEC, 12 samples (2.0%) with EIEC, 39 samples (6.6%) with EPEC, and 13 samples (2.2%) with ETEC. Among the 249 age-matched controls, 30 samples were positive for diarrheagenic E. coli. The distribution was 18 samples (7.2%) with EAEC, 11 samples (4.4%) with EPEC, and 1 sample (0.4%) with ETEC.     

Randomised primary health center based interventions to improve the diagnosis and treatment of undifferentiated fever and dengue in Vietnam

Background  

Fever is a common reason for attending primary health facilities in Vietnam. Response of health care providers to patients with fever commonly consists of making a presumptive diagnosis and proposing corresponding treatment. In Vietnam, where malaria was brought under control, viral infections, notably dengue, are the main causes of undifferentiated fever but they are often misdiagnosed and inappropriately treated with antibiotics.     

The genetic and antigenic diversity of avian influenza viruses isolated from domestic ducks, muscovy ducks, and chickens in northern and southern Vietnam, 2010–2012

To estimate the prevalence of avian influenza virus infection in Vietnam, surveillance was conducted in domestic and wild birds from households, live-bird markets, slaughtering sites, and bird sanctuaries in Vietnam between October 2010 and October 2012. Of the 4,550 samples collected, 226 influenza A virus isolates were obtained from domestic ducks, muscovy ducks, and chickens. Of these, 25 and 22 H5N1 highly pathogenic avian influenza viruses (HPAIVs) were isolated from apparently healthy domestic ducks in live-bird markets and slaughtering sites in northern and southern Vietnam, respectively. The HA genes of H5 viruses isolated from birds in northern Vietnam phylogenetically belonged to the genetic clade 2.3.2.1 and those in southern Vietnam belonged to the genetic clade 1.1. In addition, 39 H3, 12 H4, 1 H5, 93 H6, 2 H7, 18 H9, 3 H10, and 11 H11 viruses were isolated. Phylogenetic and antigenic analyses of the H6 and H9 viruses revealed that they were closely related to the isolates obtained from domestic poultry in China. Phylogenetic analyses of internal gene segments of these isolates revealed that these viruses were circulating in both domestic and wild birds in Asia and reassortment events had occurred frequently. Therefore, it will be important to continue the surveillance and strict controls over the movement and trade of poultry and poultry products in order to eradicate H5N1 HPAIV from Asia.