Prevalence and correlates of sexual behaviors among university students: a study in Hefei, China

In China, sexual health and behaviors of young people have become a growing public concern but few studies have been conducted to investigate the prevalence and psychosocial correlates of the phenomenon. A self-reported questionnaire survey on youth sexual behaviors was conducted among 1,500 university students in 2011 at Hefei, a middle-size city in eastern China. A total of 1,403 students (age = 20.30 ± 1.27 years) completed the questionnaire with a high response rate of 93.5%. Among the respondents, 12.6% (15.4% of male versus 8.6% of female) students reported having pre-marital heterosexual intercourse; 10.8% (10.5% of males versus 11.2% females) had oral sex; 2.7% (3.4% of males versus 1.7% females) reported same-sex activities; 46% (70.3% of males versus 10.8% of females) reported masturbation behaviors; 57.4% (86.2% of males versus 15.6% females) students viewed pornography. In terms of sexual communication about sexual knowledge acquisition, 13.7% (10.7% of males versus 18% of females) talked to their parents about sex; 7.1% (6.1% of males versus 8.4% of females) students reported having conversation with parents on contraception. About forcing sexual behavior, 2.7% (4% of males versus 0.9% of females) reported forcing their sexual partners to have sex, and 1.9% (2.4% of males versus 1.2% of females) reported being forced to have sex. Gender was found to be significant predictor of sexual behaviors in university students: males reported more sexual behaviors including sexual fantasy, heterosexual intercourse, masturbation, viewing pornography and talking about sex with friends. Several correlates of sexual behaviors were identified for students of different gender separately. For males, having romantic relationships, past sex education experiences, low educational aspirations, time spent on the Internet, and urban native settings were significantly associated with more sexual behaviors. For female students, having romantic relationships and urban native settings predicted sexual behaviors. Sexual behavior among University students in China is not uncommon, although there are limited ways for students to acquire sex-related knowledge: male students showed significantly more sexual behaviors than female students. Having romantic relationships and more time spent online were important predictors of sexual behaviors among university students. To guide healthy sexual behaviors in young people, comprehensive sex education programs that provide necessary sexual health knowledge about safe sex should be developed and implemented in universities in China, particularly for students who have romantic relationships and those who spend long periods of time on the Internet

High energy processes in clusters of galaxies and the origin of cosmic rays

We test the hypothesis of a universal cosmic ray intensity by calculating the secondary electron or positron production in the hadronic interactions of cosmic ray nuclei with intergalactic gas within clusters of galaxies. We find that the spectral characteristics of the radio synchrotron emission by these secondary electrons is not consistent with observations of the Coma cluster. Thus the hypothesis can be ruled out on cluster scales.published_or_final_versio

Prevalence of feline immunodeficiency virus and Toxoplasma gondii in Feral Cats on St. Kitts, West Indies

Toxoplasma gondii (T. gondii) is a cosmopolitan protozoan parasite that infects all warm-blooded species including humans. The definitive hosts of T. gondii are felid vertebrates including the domestic cat. Domestic cats shed oocysts for approximately two weeks in their feces after the primary infection. It has been shown that feline immunodeficiency virus (FIV) positive cats have a higher prevalence of and a higher titer of antibodies to T. gondii than those of FIV-negative cats. The main purposes of this study were to determine FIV prevalence and to investigate the oocysts shedding in FIV-positive and FIV-negative feral cats on St. Kitts. Fecal samples were collected from feral cats while their FIV statues were determined using a commercial SNAP kit. Total fecal DNA of each cat was tested for the presence of T. gondii DNA using a polymerase chain reaction (PCR) consistently detecting one genome equivalent. A FIV-positive status was detected in 18 of 105 (17.1%, 95% confidence interval (CI): 9.9%−24.3%) feral cats sampled. Furthermore, males were three times more likely to be FIV positive than females (p = 0.017) with an odds ratio of 3.93 (95% CI: 1.20–12.89). Adults were found to have at least twice the prevalence of FIV compared to cats younger than one year of age (p = 0.056) with an odds ratio of 3.07 (95% CI: 0.94–10.00). Toxoplasma gondii DNA was not detected in the feces of any of the 18 FIV-positive (95% CI: 0%−0.18%) and 87 FIV-negative cats (95% CI: 0%−0.04%). A follow-up study with a much bigger sample size is needed to prove or disprove the hypothesis that FIV-positive cats have a higher prevalence of shedding T. gondii oocysts than FIV-negative cats

Robust pinning of magnetic moments in pyrochlore iridates

Pyrochlore iridates A2Ir2O7 (A = rare earth elements, Y or Bi) hold great promise for realizing novel electronic and magnetic states owing to the interplay of spin-orbit coupling, electron correlation and geometrical frustration. A prominent example is the formation of all-in/all-out (AIAO)antiferromagnetic order in the Ir4+ sublattice that comprises of corner-sharing tetrahedra. Here we report on an unusual magnetic phenomenon, namely a cooling-field induced shift of magnetic hysteresis loop along magnetization axis, and its possible origin in pyrochlore iridates with non-magnetic Ir defects (e.g. Ir3+). In a simple model, we attribute the magnetic hysteresis loop to the formation of ferromagnetic droplets in the AIAO antiferromagnetic background. The weak ferromagnetism originates from canted antiferromagnetic order of the Ir4+ moments surrounding each non-magnetic Ir defect. The shift of hysteresis loop can be understood quantitatively based on an exchange-bias like effect in which the moments at the shell of the FM droplets are pinned by the AIAO AFM background via mainly the Heisenberg (J) and Dzyaloshinsky-Moriya (D) interactions. The magnetic pinning is stable and robust against the sweeping cycle and sweeping field up to 35 T, which is possibly related to the magnetic octupolar nature of the AIAO order.Comment: 16 pages, 4 figure

Dynamic changes of soil organic carbon under different land use type in Sanjiang Plain

The Sanjiang Plain in the northeast part of Heilongjiang Province is one of the largest freshwater marshes in China, which has been experienced intensive cultivation over past 50years. To understand the dynamic changes of soil organic carbon (SOC) after different durations of cultivation, soil samples down to a depth of 120 cm were collected in layers from the lowland and upland fields having been reclaimed for 5-25 years, with adjacent undisturbed wetland and forestland as the control. The study of the vertical distribution of SOC and its relationship with soil pH showed that the SOC content in undisturbed wetland and cultivated lowland rice fields had a marked decrease企om0-10 cm to 40-60 cm and a less change downward, and a similar variation trend was observed in undisturbed forestland and cultivated soybean fields, only with the difference that the SOC content in 0-10cm layer was much higher in forestland than in wetland, and lower in soybean fields than in rice fields. For undisturbed wetland, its SOC content in surface layer was decreased by 49.3% and 14.3% after claimed for 10 and 25 years, and for undisturbed forestland, 81.9% and 68.3% of its SOC in surface layer were lost after reclaimed for 5 years and 18 years, respectively. The soil pH in surface layer was decreased in the sequences of undisturbed wetland > lowland rice field reclaimed for 25 years > lowland rice field reclaimed for 10 years, and soybean field reclaimed for 5 years > soybean field reclaimed for 18 years > undisturbed forestland. All of these suggested that reclamation made a great loss of SOC in surface layer both in wetland and forestland, and the SOC loss was much greater in forestland than in wetland. The variation of surface soil pH under reclamation could be one of the factors inducing the SOC loss, and a longer period of reclamation combining with rational management could be favorable to the stabilization of SOC

Quantum-well resonances caused by partial confinement in MgO-based magnetic tunnel junctions

Quantum-well resonance is achieved through partial confinement in magnetic tunnel junctions (MTJs), which provides an additional operable degree of freedom to regulate quantum-well levels. Using Al/Fe/MgO/Fe/Al and Ag/Al/Fe/MgO/Fe/Al/Ag MTJs as examples, via first-principles calculations, we demonstrate that the partial confinement of $\Delta_1$ electron at Al/Fe interface and the full confinement at Fe/MgO interface combine to produce quantum-well resonances in Fe. The quantum-well levels of Fe can be periodically adjusted by two degrees of freedom: Fe and Al thickness. The oscillation period obtained from conductance $G_{\uparrow\uparrow}$ is 2.13 ML Fe (9 ML Al), close to 2.25 ML Fe (8.33 ML Al) calculated by bcc-Fe (fcc-Al) band. The combination of long and short periods enables quantum-well levels to be finely adjusted. An ultrahigh optimistic TMR effect of $3.05\times10$$^5$\% is achieved. Our results provides a new path for designing and applying quantum-well resonances in spintronics devices

BL Lacertae are probable sources of the observed ultra-high energy cosmic rays

We calculate angular correlation function between ultra-high energy cosmic rays (UHECR) observed by Yakutsk and AGASA experiments, and most powerful BL Lacertae objects. We find significant correlations which correspond to the probability of statistical fluctuation less than $10^{-4}$, including penatly for selecting the subset of brightest BL Lacs. We conclude that some of BL Lacs are sources of the observed UHECR and present a list of most probable candidates.Comment: Replaced with the version accepted for publication in JETP Let