Intake fraction is a new concept applied in assessing human health effect of pollutants. In the present paper, the history and practical use of it were reviewed, and then the calculation of it was also analyzed. After illustrating and discussing previous approaches for estimating intake fraction, the calculation can be classified into two sorts: one is taking the spatial area as the object, and the other is taking the people as the object. The latter is more fitful to estimate the intake fraction of mobile emission, in which it is necessary to investigate the related population and then combine the time-activity patterns with the microenvironment concentrations, in addition, modeling microenvironmental concentrations is critical for the calculation of intake fraction.

Objective:To examine the influence of exam stress on the sustained attention of students with different levels of trait anxiety. Methods: With the State-Trait Anxiety Inventory (STAI), 10 students with high trait anxiety (high trait anxiety group, H group) and 10 with non-high trait anxiety (non-high trait anxiety group, NH group) were randomly sampled from 400 students taking the coming College English Test-Band 4 (CET-4). Their attention was measured with digit cancellation test and the event related potentials during the control phase (the period was chosen 2 weeks after the beginning of the semester and there was no examination in the following 3 months) and the stress phase ( from 2 weeks to 1 day before CET-4 examination). Results: The right cancellation number of the NH group was higher than that of the H group(F=8.178, P=0.007). During the control phase the P300 amplitude and latency were similar between the 2 groups (F= 0.125, 0.127, respectively;P= 0.728, 0.726, respectively). During stress phase the P300 amplitude of the H group was significantly lower than that of the NH group(F=12.913, P=0.002)and the P300 latency of the H groups was longer than that of the NH group(F=16.952, P= 0.001). In NH group, the P300 latency in the stress phase was significantly shorter than that of the control phase (F= 6.514, P=0.020). Conclusion: Exam stress has different influences on the sustained attention of people with different levels of trait anxiety, which suggests that people with high trait anxiety are the target population for stress management.

Objective To investigate the clinical value of susceptibility weighted imaging (SWI)combined with three dimensional pseudo continuous arterial spin labeling (3D-PCASL)on the prognosis analysis of acute cerebral infarction.Methods Thirty cases with acute cerebral infarction (< 72 h)underwent conventional MRI,MRA,3D-PCASL and SWI.NIHSS scores were performed at the time of examination and 3 months later.The correlation between the collateral blood vessels,regional cerebral blood flow (rCBF)detected by combination of SWI and 3D-PCASL with clinical prognosis were analyzed.Results Twenty-three cases showed collateral blood vessels in the lesions with 1 grade in 14,and 2 grade in 9.The average rCBFs in grade 0,1,2 infarction areas were (22.69±11.94)mL·100 g-1 ·min-1 ,(25.10±16.55)mL·100 g-1 ·min-1 and (33.04±24.24)mL·100 g-1 ·min-1 ,respectively.Collateral blood vessels,rCBF were positive correlated with the NIHSS scores (r=0.989,P< 0.01).18 cases showed multiple vessels around the lesions. The average rCBFs in the infarction area with or not with periphery collateral blood vessles were (28.33±24.24)mL·100 g-1 ·min-1 and (22.69±11.94)mL·100 g-1 ·min-1 ,respectively.There was a positive correlation between rCBF and NIHSS scores (r=0.897,P<0.01). Of 30 cases of acute cerebral infarction,the average CBFs in the infarct areas and the contralateral mirror areas were (26.92±18.22)mL·100 g-1 · min-1 and (34.22±12.37)mL·100 g-1 ·min-1 .There was significant difference (t=8.093,P<0.01).Conclusion The combination of SWI and 3D-PCASL can display the collateral blood vessels in the lesions and soft meninges,and provide the quantitative analysis of rCBF,which has important clinical significance for prediction of the prognosis of acute cerebral infarction.

Objective Studies have shown that problem based learning (PBL) can improve the students' ability of autonomous learning.However,it is unclear whether students' autonomous learning ability will affect students' evaluation in PBL teaching.This study took medical psychology course as an example to explore the influence of medical students' autonomous learning ability on PBL teaching effect.Methods 43 8-year program medical students of Grade 2010 and 2011 were enrolled in this study.Scale was used to assess medical students' autonomous learning ability before the start of the PBL teaching.Self made questionnaire was used to survey the students' evaluation in PBL teaching.Linear correlation analysis was used to detect the relationship between medical students' autonomous learning ability and students' evaluation in PBL teaching and their examination results.Results Medical students' autonomous leaming ability is significantly positively correlated to the students' evaluation of PBL teaching (P＜0.05).The correlation coefficient between learning motivation and "PBL enhanced learning interest" or "PBL enhanced information utilization ability" was high (r=0.507 and 0.536,respectively).It showed that students with stronger autonomous learning ability had more positive evaluation of PBL teaching.The students' learning motivation was also positively correlated to the test score (r=0.416,P=0.006).Students with stronger learning motivation had higher test score in the final exam.Conclusion These results indicate that the relationship between the students' autonomous learning ability and PBL teaching is bidirectional.The students with more powerful ability of autonomous learning will be more active in the process of PBL teaching,and the positive experience will promote their autonomous learning ability in turn.

Objective To explore the diagnostic value of helical CT,fluid attenuated inversion recovery(FLAIR),magnetic resonance angiography (MRA)and susceptibility weighted imaging (SWI)at 3.0T MR for acute ischemic stroke (AIS).Methods 48 cases of AIS(<72 h)underwent conventional CT,MRI,MRA and SWI.The correlations between hyperdense middle cerebral artery sign (HMCAS),proximal hyperintense vessel sign(HVS),magnetic sensitive spatially-integrated susceptibility vessel sign(SVS),vascular dot middle cerebral artery sign(DMCAS),distal HVS and collateral circulation of the blood vessels surrounding leptomeninges expansion degree were analyzed.Results In 48 AIS cases,HMCAS were showed in 18(37.5%),DMCAS 12(25.0%),proximal HVS 33(68.7%), distal HVS 40(83.3%),SVS 43(89.6%)and surrounding soft meningeal vascular 39(81.2%).The difference between spatially-integrated SVS and HVS was statistically significant (P<0.05);For HVS and HMCAS responsibility blood vessels at the bottom,the difference was statistically significant(P<0.01).For pia mater lesions around the blood vessel and distal HVS display degree,the responsibility of the blood vessels was high consistency(P=0.789).The difference between MCA distal HVS and DMCAS was statistically significant (P<0.01).Conclusion It has obvious consistency for SVS,proximal HVS and HMCAS of MCA on the responsibility of AIS.SWI is better than FLAIR and CT.It has obvious statistical sighificance between DMCAS,HVS and surrounding leptomenings vasodilatiov.