[Development of Risk Assessment Index System on HIV infection among young students based on Delphi method].

Objective: To develop a Risk Assessment Index System (RAIS) on HIV infection among young students based on Delphi method and to provide individual HIV infection risk assessment, targeted prevention and control measures. Methods: Delphi method was applied to determine the index system and weight of the assessment tool through three rounds of expert consultation and overall consideration of opinions and suggestions from 19 experts. Results: The positivity coefficients of three rounds of expert consultation were 100%. The authority coefficient of experts was between 0.887 and 0.945. The Kendall's W coefficients through first, second and third round specialist consultation was 0.379, 0.329 and 0.248, respectively (all P<0.001). The coefficients of variation in the third round were all less than 0.25, indicating that experts' opinion tend to be consistent and the results are highly reliable. The HIV infection risk assessment index system among young students consisted of 7 first grade indices and 54 second grade indices, of which weight was calculated. Conclusions: The RAIS on HIV infection for young students was initially established based on Delphi method, and could be used in the development of HIV infection risk assessment tools for personalized prevention and intervention among young students. However, the reliability, validity and effect of this assessment index system need to be further evaluated.

[Cluster analysis on survey of sexual health characteristics and health education demands in young students].

Objective: To explore the difference of sexual health characteristics and demands in students in different groups, and provide the basis for targeted sexual health eduction for AIDS prevention in young students. Methods: A survey was conducted based on the requirement of health education about sexual health and AIDS prevention in young students by the education department of Guangdong province. A two-step cluster analysis was performed on the survey data obtained by convenient sampling, the variables and number of clusters included were determined by combination of analysis results and professional knowledge. The demographic characteristics, the content and form of sexual health education needed were compared among different groups. Results: Survey data of 3 884 students were collected, and six variables were used for classification: cognition or occurrence masturbation, sexual behavior, frequency of sexual information acquisition, number of acceptable sex partners and AIDS knowledge awareness rate. By these variables, the students were classified into three levels of risk groups: high risk group (46.6%), medium risk group (39.9%) and low risk group (13.5%). As for demographic characteristics, high risk group, with a median age of 19 years, had the highest proportions of boys (65.9%), students with non-heterosexuality orientation (15.2%), urban residents (58.2%), only children (30.8%) and undergraduates (54.7%). Medium risk group, with a median age of 19 years, had the highest proportions of girls (82.7%) and vocational college students (34.0%). Low risk group, with a median age of 18 years, had the highest proportions of rural residents (52.4%), non-only child (80.6%), senior high school students (41.3%), non-boarding students (17.5%) and students without internship and part-time job experience (43.2%). In terms of health education demands, high risk group had a higher demand of information about self-identity, sexual safety, sexual decision making, contraception, abortion, and sexually transmitted disease or AIDS prevention. Medium risk group paid more attention to value on love and marriage, sexual assault. Low risk group showed a higher demand of adolescent physiology knowledge. Compared with low risk group, high risk group had a higher demand of peer education, Internet/multimedia, anonymous counseling and other forms of sexual health education. The differences were significant. Conclusion: The characteristics, sexual knowledge awareness, attitude and behavior, and health education demands of young students in different groups are different, so health education materials and methods should be developed according to the characteristics of different groups to enhance the acceptance and enthusiasm of students and improve the quality of sexual health education.

[Analysis on influencing factors of HIV testing services utilization in students with self-assessed high risk of HIV infection based on Andersen's model].

Objective: To analyze the influencing factors for HIV testing services utilization in students with self-assessed high risk of HIV infection. Methods: The research framework of the influencing factors for HIV testing services utilization in students was developed based on Andersen's health services utilization behavioral model and related literature. A cross-sectional survey was performed in students with self-assessed high risk of HIV infection by an online HIV infection risk assessment tool from March to April 2019. Multiple logistic regressions were applied with hierarchical model. Results: A total of 526 students were included in the study (age: 19.30±1.19 years old), in whom 96.2% agreed that HIV testing should be received after high-risk behavior. 56.7% (298/526) had sexual behavior and the HIV testing rate was 11.0% (58/526). The HIV testing rates in students who had and had no sex behavior were 13.42%(40/298) and 7.89% (18/228), respectively. According to the results from multivariate logistic regression analysis, non-heterosexual (compared with heterosexual, OR=7.88, 95%CI: 3.98-15.61) and higher score of AIDS knowledge awareness (compared with lower score, OR=2.05, 95%CI: 1.07-3.93) in propensity factor module, and having risk sexual behavior (compared with having no risk sexual behavior, OR=2.66, 95%CI: 1.41-5.03) and having diagnosis of STD infection in hospital (compared with having no such diagnosis, OR=6.35, 95%CI: 2.21-18.27) in demand factor module, and receiving health education about AIDS prevention in the past year (compared with receiving no such health education, OR=0.29, 95%CI: 0.11-0.76) and receiving health education about AIDS testing service in the past year (compared with receiving no such health education, OR=3.67, 95%CI: 1.71-7.90) in ability factor module were the influencing factors for utilization of HIV testing services. Conclusions: The acceptance of HIV testing in students needs to be improved urgently. Propensity factors, such as their AIDS knowledge awareness and sexual orientation, and demand factors, such as having risk sexual behavior and STD infection, have obvious impacts on the utilization of HIV testing services. However, health education about AIDS prevention and HIV testing service can play a more important role in facilitating the utilization of HIV testing in students. In the future, we should further strengthen the publicity of voluntary HIV counseling and testing service in students with particular attention to girls and those with risk sexual behaviors.

[Influence of self-categorized deviation in knowledge, attitude and practice for sexual health on the willingness to seek help for corresponding problems among young students].

Objective: To evaluate the effect of "self-categorization" on decision of health preference and the influence of self-categorized deviation in knowledge, attitude and practice (KAP) on the willingness of seeking help for sexual health among young students. Methods: From March to April 2019, young students who used a WeChat applet for sexual health and HIV infection risk assessment, which is called "Detective Bear" were recruited and investigated. According to the consistency between the self-categorization of KAP for sexual health and the systematic categorization from their honest answers, the participants were allocated into three groups: consistent, low or high status, according to their judgment on sexual information acquisition, sexual attitude, and the actual number of sexual experiences. Logistic regression was used to analyze the differences in the willingness to seek help for sexual health problems between the three groups. Results: 2 009 students with an average age of (19.2±1.1) were included. 54.7% (1 099/2 009) were female, and 98.4% (1 976/2 009) were college, undergraduate or postgraduate students. 49.0% (984/2 009) were in the consistent group, 10.9% (219/2 009) had a lower self-categorization, 40.1% (806/2 009) had a higher self-categorization. Compared with the consistent group, students with lower self-categorization of KAP for sexual health were less likely to assess HIV voluntary counseling and testing (aOR=0.65, 95%CI: 0.43-0.99). However, students with higher self-categorization seemed to dislike seeking help for sexually transmitted diseases (aOR=0.76, 95%CI: 0.59-0.98). Conclusions: Deviation in self-categorization of KAP for sexual health will reduce the young students' willingness to seek help for related problems. Especially those with lower self-categorization, lack of risk consciousness, and refuse to assess counseling and testing may increase the HIV/AIDS epidemic among this population. It is necessary to strengthen the capacity of self-assessment for young students while promoting sex education.

[Design and analysis of testing results of a WeChat applet for sexual health and HIV infection risk assessment in young students].

Objective: To summarize the design and analysis of testing results of a WeChat applet, which is called "Detective Bear", for sexual health and HIV infection risk assessment in young students, and evaluate its feasibility and effectiveness. Methods: Based on self-categorization theory, by using cluster analysis and Delphi expert consulting method, the framework of WeChat applet, risk assessment index system and preventive intervention content were determined. Young students were recruited by student associations for the application test, the results of the repeated tests and the satisfaction survey were collected and analyzed. Results: The study included 393 participants who repeated the test twice and 750 participants who volunteered to participate in the satisfaction questionnaire survey. The applet contains five modules: self-role judgment, self-test, risk assessment, assessment report generation and background management. The risk assessment module contains 6 first-level indicators and 55 second-level indicators. Assessment report generation module includes role diagnosis type, radar chart of HIV sexual health KAP and intervention prescription. In 393 students who repeated the test, the awareness of AIDS to be a serious sexually transmitted disease, the epidemic trend in young students in China, with active seeking HIV testing services and caring the infected improved. The satisfaction survey showed that 75.7% of students (568/750) accepted the applet, 86.5% (649/750) agreed the evaluation report, 83.1%(623/750) thought that there were some problems, but it was easy to use, 93.3% (700/750) said they can learn something from the applet and 84.1% (631/750) satisfied with the page design. Some students thought the questionnaire was too long and somewhat difficult to complete (P<0.05), and some reported that more can be learned (P<0.05). Conclusions: The applet integrates AIDS prevention related knowledge and practice into a challenging, interesting, interactive game and provide individualized, concrete risk assessment and self-intervention for young students, which can effectively help students to improve the awareness of AIDS related knowledge and get links for access to condoms, testing and other intervention services. However, its large-scale application and long-term effect need to be further tested.

[Contagiousness and secondary attack rate of 2019 novel coronavirus based on cluster epidemics of COVID-19 in Guangzhou].

Objective: To analyze the contagiousness and secondary attack rate of 2019 novel coronavirus in cluster epidemics in Guangzhou and provide evidence for the prevention and control of COVID-19. Methods: All the individuals identified to be infected with 2019-nCoV in Guangzhou, including confirmed cases and asymptomatic cases, were included and classified as imported cases and local cases. The first case of each cluster epidemic was defined as index case, and the number of subsequent infections was calculated to evaluate the contagiousness and secondary attack rate of 2019 novel coronavirus in the shortest incubation period of 1-3 days. Results: As of 18 February, 2020, a total of 349 cases of 2019-nCoV infection, including 339 confirmed cases (97.13%) and 10 asymptomatic cases (2.87%) were reported in Guangzhou. There were 68 clusters involving 217 2019-nCoV infection cases (210 confirmed cases and 7 asymptomatic cases). The median number of subsequent infections caused by an index case in a cluster epidemic was 3, among which 2 were confirmed cases and 1 was asymptomatic cases, respectively. The average number of contagiousness was 2.18 in shorted incubation period of 1-3 days (The average number of infected cases were 2.18 cases by the index case in a cluster epidemic), the average infection number in family members was 1.86, and the infection ratio of family member transmission was 85.32% (1.86/2.18). The secondary attack rate in close contacts with shortest incubation period of 1-3 days was 17.12%-18.99%, the secondary attack rate in family members was 46.11%-49.56%. Conclusions: The cluster epidemic of COVID-19 in Guangzhou mainly occurred in families, the contagiousness was high. It is necessary to strengthen the prevention and control to reduce the community transmission of COVID-19.

[Status quo and characteristic analysis among MSM-users of the "Internet Plus-based AIDS Comprehensive Prevention Service System" in Guangzhou].

Objective: To analyze the characteristics of the "Interner Plus-based AIDS Comprehensive Prevention Service System" among MSM who frequently using the Internet in Guangzhou. Methods: An online survey was conducted among MSM who were recruited through gay-website portals between August and September, 2018 in Guangzhou, to collect information regarding the use of and attitudes on the "Interner Plus-based AIDS Comprehensive Prevention Service System" . Logistic regression was used to explore the association between the use of Internet intervention tools and related behavioral characteristics. Information on the awareness of AIDS, HIV testing, and condomless anal sex behavior were compared between the core or non-core services users. Results: A total of 777 Internet-based MSM were recruited as participants including 638 men (82.1%) as core service users. MSM were satisfied in using the the "Interner Plus-based AIDS Comprehensive Prevention Service System" while more than 80.0% of the users felt that the tools were helpful in: increasing the HIV awareness, promoting test uptake, and reducing those related risk behavior. Comparing with those who did not use the tools, the users showed higher rates in practising condomless anal intercourse (1.50-1.86 times), commercial sex with men (11.60-21.21 times), and unprotected vaginal intercourse (13.62-20.67 times), in the last 6 months. Proportions of core service users appeared as: [96.6% vs. 74.8%, aOR (95%CI): 8.80 (4.85-15.97)] on HIV testing, [56.4% vs. 22.3%, aOR (95%CI): 4.54 (2.94-7.02)] on regular HIV testing and [86.2% vs. 80.6%, aOR (95%CI): 1.75 (1.06-2.89)] on awareness of HIV knowledge respectively, which were all significantly higher than the non-core service users. Conclusions: The frequent Internet using MSM in Guangzhou claimed to have had high acceptance and satisfaction on the local Internet HIV intervention service tools. The "Internet Plus-based AIDS Comprehensive Prevention Service System" had effectively reached the high-risk subgroups of MSM, increasing the awareness on related risk and promoting testing on HIV.

[Characteristic analysis among MSM-users of the "Online HIV Acquisition Risk Assessment System" in Guangzhou].

Objective: To analyze the characteristics of levels related to the risk through self-evaluation system, among MSM users in Guangzhou, between 2015 and 2017. Methods: Between 2015 and 2017, data was collected from the users of a self-evaluation system network related to HIV infection, based on the previous 'HIV health risk appraisal model'. Information on risk factors was collected to calculate the scores and levels of risks and to estimate the incidence of HIV. Taking the reference of R value on risks as (R=0.9-1.1) in general population. The ones with very low risk, with low risk, moderate risk, high risk and very high risk were set as R≤0.5, 0.52.0, respectively. The scores of modifiable risk factors were compared with different subgroups of MSM. Results: A total of 4 601 MSM were involved in this study, with the following features presented as: aged 16-64 (28.38±7.11) years, proportions of residence from Guangzhou, Guangdong province or other provinces as 38.6%(1 776/4 601)、35.4%(1 629/4 601) and 26.0%(1 197/4 601), 59.6%(2 742/4 601) received bachelor or above degrees. 81.3%(3 741/4 601) of them claimed as having homosexual orientation. R values of risk level on very low risk, low risk level, moderate risk, high risk and very high risk appeared as 12.9%(594/4 601), 50.9%(2 342/4 601), 17.0%(783/4 601), 14.8%(682/4 601) and 4.3%(200/4 601), respectively. Scores of modifiable risk factors decreased year by year (P<0.05), among MSM in this study. In either of the groups that experiencing insertive or receptive sex, the ones with heterosexual orientation presented the highest scores of modifiable risk factors (P<0.05). Conclusions: The risk levels on HIV infections called for special attention among the users of the self-evaluation network system. Among the MSM that carrying either insertive or receptive sex role, the ones with heterosexual orientation had the highest risk levels and scores of modifiable risk factors in Guangzhou. Further study should be explored to better understand the causes of related risks.

[Applicability and feasibility of "Lingnanzhun" -an "Internet Plus-based HIV Self-testing Tool" targeting MSM in Guangzhou].

Objective: This article was to evaluate the applicability and feasibility of "Lingnanzhun" -an "Internet Plus-based HIV Self-testing Tool" targeting MSM in Guangzhou. Hopefully, the results could be used to improve the existing HIV testing services and to support the implementation and scale-up of HIV self-testing programs. Methods: Data were collected from a survey on HIV testing preferences among the Internet-using MSM in April to June, 2015. Univariate and multivariate logistic regression analysis were applied to identify factors associated with the use of HIV self-testing service provided by Lingnanzhun. Information related to the users of Lingnanzhun during September 2014 and December 2018 was also collected. Results: 769 MSM were recruited as participants. Of them, age distribution was 16-77(28.6±6.8) years old, 88.3%(679/769) were unmarried, 42.2%(325/769) were registered residents of Guangzhou, 82.1%(631/769) had university or college education. Among them, 195 (25.4%) used the HIV self- testing program of Lingnanzhun while 574 (74.6%) using the clinic service. Compared with the clinic service users, the Lingnanzhun users showed the following characteristics: longer experience in the MSM community ≥10 years (32.8% vs. 20.9%, 64/195 vs. 120/574); having male casual sexual partners ≥2 (42.1% vs. 29.6%, 82/195 vs. 170/574); having group sex (6.2% vs. 2.6%, 12/195 vs. 15/574) and having commercial sex with men (13.8% vs. 3.0%, 27/195 vs. 17/574). Data from the Lingnanzhun users showed that a total of 3 000 users had practised 5 038 times of self HIV-testings. 11.4% (343/3 000) of the Lingnanzhun users had never been tested. Conclusions: It was applicable and feasible to provide Internet-based HIV self-testing service to MSM as a significant complement to the traditional facility-based HIV testing services. It was also useful in accessing those who were having higher risk or had never received HIV testing so as to increase the testing uptake and the frequency.

[Effectiveness of the "Internet Plus-based AIDS Comprehensive Prevention Service System" among MSM in Guangzhou].

Objective: To evaluate the effectiveness of the "Internet Plus-based AIDS Comprehensive Prevention Service System" among men who have sex with men in Guangzhou. Methods: Data through case-reporting and follow-up programs on MSM HIV/AIDS in Guangzhou was collected from the China Information System for Disease Control and Prevention, which including those from the referral and follow-up treatment compliance programs in 2008-2014 (pre-treatment) and 2017-2018 (post-treatment). According to the types of care services, three groups were set as: with "Internet Plus" service, with 'HIV counseling/testing service' or with 'routine medical service'. General Estimating Equation (GEE) was used to analyze the follow up situation of HIV/AIDS cases, annually. Cox proportional hazard regression model was used to analyze the proportions of treatment referral, within the 30 days of diagnosis. Results: Before the implementation of immediate treatment after HIV diagnosis, 90.6% (707/780) of the HIV/AIDS cases received the first follow up program including the CD(4)(+) T cells counts (CD(4)) test service within 90 days of diagnosis, in the "Internet Plus-based HIV/AIDS care service" group presented 1.19 times (95%CI: 1.14-1.25) of the routine medical service group. The implementation of immediate treatment after HIV diagnosis, compared with the routine medical service group, the "Internet Plus" service group presented 1.71 times (95%CI: 1.03- 2.83) more treatment referrals within the 30 days of diagnosis, when the first testing CD(4) was ≤200 cells/µl. Compared with the routine medical service group, the HIV counseling and testing service group showed 1.37 times (95%CI: 1.20-1.56) more of the treatment referrals within the 30 days of HIV diagnosis, after the first testing CD(4) counts as >200 cells/µl. Conclusion: Standardized care and follow-up service should be promoted as soon as the referral and treatment programs were set after the diagnosis was made, under the "Internet Plus-based AIDS Comprehensive Prevention Service System" for the MSM population, in Guangzhou.

[Prevalence of drug resistance in treatment-naive HIV infected men who have sex with men in Guangzhou, 2008-2015].

Objective: To understand the prevalence of drug resistance in treatment-naive HIV infected men who have sex with (MSM) in Guangzhou. Methods: HIV-1 RNA were extracted from the serum specimens of the MSM newly confirmed to be HIV-1 positive, living in Guangzhou and receiving no anti-viral therapy from 2008 to 2015. HIV-1 pol gene segments, including full protease and part reverse transcriptase, were amplified by nested reverse transcription polymerase chain reaction (nested-PCR) and sequenced by Sanger. Subsequently, the sequence data were submitted to Stanford University HIV Drug Resistance Database for drug resistance analysis. Results: Among 2 283 HIV infected MSM, HIV-1 pol gene segments were obtained from the serum samples of 1 986 HIV infected MSM aged 16-84 (30.18±8.24) years. Among them, the unmarried accounted for 74.17% (1 473/1 986), those of Han ethnic group accounted for 90.64% (1 800/1 986), those with education level of college or above accounted for 49.65% (986/1 986), those with education level of senior high school or secondary school accounted for 27.14% (539/1 986), those with education level of junior high school or below accounted for 20.89% (415/1 986). The distribution of subtypes was predominated by CRF07_BC (38.22%, 759/1 986) and CRF01_AE (34.49%, 685/1 986). The overall prevalence of drug resistance was 3.32% (66/1 986). The prevalence of resistance to protease inhibitors (PIs), nucleoside reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) were 1.36%(27/1 986), 0.65% (13/1 986) and 1.61% (32/1 986), respectively. Subtype B had higher resistance to PIs, NRTIs and NNRTIs and subtype CRF55_01B had highest resistance to NNRTIs compared with other subtypes. In subtype B, the resistant rates to D4T, EFV and NVP were highest (all 4.17%, 5/120), followed by those to NFV, AZT and RPV (all 3.33%, 4/120). In subtype CRF55_01B, the resistant rates to EFV and NVP were highest (all 5.50%, 16/291), followed by those to ETR and RPV (all 5.15%, 15/291). Conclusions: The prevalence of drug resistance in treatment-naive HIV infected MSM in Guangzhou remained at low level and current antiretroviral drugs are generally effective. However, subtype B and CRF55_01B have higher drug resistance.

[Characteristics and influencing factors regarding social relations among men who have sex with men].

Objective: To study the characteristics of social relations and relative factors among MSM in Guangzhou. Methods: Data was collected through a cross-sectional study in Guangzhou from November 2016 to May 2017. Sample size was estimated and participants were recruited from the voluntary counseling and testing services (VCT) which were set for MSM population, by nongovernmental organizations (NGOs) and the Centers for Disease Control and Prevention (CDC). Social ties and demographic characteristics of the respondents and their sexual partners were analyzed through both Chi square test and generalized estimating equations (GEE). Results: A total of 1 073 MSM, together with their nominated 4 301 partners were successfully recruited and involved in this study. Age (OR=1.2, P=0.01) and non-internet based intercourse (OR=1.65, P<0.01) were easy to form close relation with strong ties. Compared with MSM traditional venues (chess and cards room, tea room bathhouse, club), general public venue (bars, KTV, parks, shopping malls, schools, restaurants) (OR=1.46-3.12, P<0.01) showed close relation with strong ties. Our finding showed that MSM at the age of 18-25 preferred to build weak ties with the older MSM, while the 26-30-year-olds and 31-40-year-olds prefer to establish weak ties with younger partners but the 41-50-year-olds preferred to develop weak ties with one that were ten years younger. Conclusions: Clusters were noticed in the MSM populations when grouping and making friends with ones at different age. Characteristics regarding the relationship between sexual partners in choosing venues and ways of dating were different. Targeted intervention programs need to be explored innovatively.

[Commuting mode specific exposure to PM(2.5) in urban area of Guangzhou].

Objective: To find the differences in PM(2.5) exposure level in the context of four commuting modes (by walk, bicycle, bus and subway) in Guangzhou. Methods: The PM(2.5) exposure assessment was carried out from January to December 2015 in Guangzhou. PM(2.5) was measured by using SidePak individual dust meter (AM510, TSI Inc. USA) with time interval of 1 minute. Our measurement was taken on Monday, Wednesday, Friday and Sunday in the second week of each month and the samples were collected in the morning (07:00-09:00), afternoon (11:00-13:00) and evening (17:00-19:00). Results: A total of 284 air samples during walking, 281 air samples during bicycle riding, 278 air samples in bus, and 280 air samples in subway were collected. The median PM(2.5) concentrations exposed during walking, during bicycle riding, in bus and in subway were 38.4, 38.6, 23.3 and 24.1 µg/m(3), respectively, which were positive correlated with exposure concentration in fixed surveillance sites. The exposure level was lowest in summer, and highest in winter. The median of one-way exposure level to PM(2.5) from high to low were as follows: 21.0 µg for bicycle riding, 20.1 µg for walking, 5.1 µg for taking bus and 2.6 µg for taking subway. The season and time specific one-way exposure levels to PM(2.5) of four commuting modes were consistent. Conclusions: The exposure level to PM(2.5) was obviously higher during walking and bicycle riding than that in bus and subway. The exposure level to PM(2.5) during walking was higher than that during bicycle riding, in bus and in subway.

Cancer-initiating cells derived from human rectal adenocarcinoma tissues carry mesenchymal phenotypes and resist drug therapies.

Accumulating evidence indicates that cancer-initiating cells (CICs) are responsible for cancer initiation, relapse, and metastasis. Colorectal carcinoma (CRC) is typically classified into proximal colon, distal colon, and rectal cancer. The gradual changes in CRC molecular features within the bowel may have considerable implications in colon and rectal CICs. Unfortunately, limited information is available on CICs derived from rectal cancer, although colon CICs have been described. Here we identified rectal CICs (R-CICs) that possess differentiation potential in tumors derived from patients with rectal adenocarcinoma. The R-CICs carried both CD44 and CD54 surface markers, while R-CICs and their immediate progenies carried potential epithelial-mesenchymal transition characteristics. These R-CICs generated tumors similar to their tumor of origin when injected into immunodeficient mice, differentiated into rectal epithelial cells in vitro, and were capable of self-renewal both in vitro and in vivo. More importantly, subpopulations of R-CICs resisted both 5-fluorouracil/calcium folinate/oxaliplatin (FolFox) and cetuximab treatment, which are the most common therapeutic regimens used for patients with advanced or metastatic rectal cancer. Thus, the identification, expansion, and properties of R-CICs provide an ideal cellular model to further investigate tumor progression and determine therapeutic resistance in these patients.

The Co-film-thickness dependent lateral photoeffect in Co-SiO2-Si metal-oxide-semiconductor structures.

We report a transient lateral photoeffect (LPE) in thin metallic Co films deposited on n-type Si substrates with native SiO(2) surfaces. Under the nonuniform irradiation of a laser beam, the lateral phtovoltage (LPV) shows high sensitivity to the laser position in the metal film plane. This effect can be interpreted by the metal-semiconductor (MS) junction formed between metal and semiconductor. The LPV depends significantly on the thickness of Co film. The position sensitivity shows a peak value of 42.6 mV/mm for Co(2.8mn)-SiO(2)-Si and decreases greatly with the increase of the Co film thickness. We explain that by the shorting effect of the metallic film.

Nonlinear response and optical limiting in SrBi(2)Ta(2)O(9) thin films.

SrBi(2)Ta(2)O(9) (SBT) thin films on quartz substrates were prepared by use of the pulsed-laser deposition technique. The nonlinear refractive indices, n(2) , of the SBT films were measured by use of z-scan techniques with picosecond pulses. Large negative nonlinear refractive indices of 3.84 and 3.58cm(2)/GW were obtained for the wavelengths 532 nm and 1.064mum , respectively. The two-photon absorption coefficient was determined to be 7.3 cm/GW for 532 nm. The limiting behavior of SBT thin film on a quartz substrate was investigated in an f/5 defocusing geometry by use of 38-ps-duration, 532-nm, 1.064mum laser excitation.

The PAS superfamily: sensors of environmental and developmental signals.

Over the past decade, PAS domains have been identified in dozens of signal transduction molecules and various forms have been found in animals, plants, and prokaryotes. In this review, we summarize this rapidly expanding research area by providing a detailed description of three signal transduction pathways that utilize PAS protein heterodimers to drive their transcriptional output. It is hoped that these model pathways can provide a framework for use in understanding the biology of the less well-understood members of this emerging superfamily, as well as of those to be characterized in the days to come. We use this review to develop the idea that most eukaryotic PAS proteins can be classified by functional similarities, as well as by predicted phylogenetic relationships. We focus on the alpha-class proteins, which often act as sensors of environmental signals, and the beta-class proteins, which typically act as broad-spectrum partners that target these heterodimers to their genomic targets.