Characterization and Identification of MicroRNA Core Promoters in Four Model Species

MicroRNAs are short, noncoding RNAs that play important roles in post-transcriptional gene regulation. Although many functions of microRNAs in plants and animals have been revealed in recent years, the transcriptional mechanism of microRNA genes is not well-understood. To elucidate the transcriptional regulation of microRNA genes, we study and characterize, in a genome scale, the promoters of intergenic microRNA genes in Caenorhabditis elegans, Homo sapiens, Arabidopsis thaliana, and Oryza sativa. We show that most known microRNA genes in these four species have the same type of promoters as protein-coding genes have. To further characterize the promoters of microRNA genes, we developed a novel promoter prediction method, called common query voting (CoVote), which is more effective than available promoter prediction methods. Using this new method, we identify putative core promoters of most known microRNA genes in the four model species. Moreover, we characterize the promoters of microRNA genes in these four species. We discover many significant, characteristic sequence motifs in these core promoters, several of which match or resemble the known cis-acting elements for transcription initiation. Among these motifs, some are conserved across different species while some are specific to microRNA genes of individual species

Observation of Small Polaron and Acoustic Phonon Coupling in Ultrathin La0.7Sr0.3MnO3/SrTiO3 Structures

Understanding the underlying physics of interactions among various quasi-particles is a fundamental issue for the application of spintronics and photonics. Here the observation of a coupling between the small polarons in the nanoscale ultrathin La0.7Sr0.3MnO3 (LSMO) films and the acoustic phonons in the SrTiO3 (STO) substrate using ultrafast pump–probe spectroscopy has been reported. According to the temperature- and wavelength-dependent measurements, the amplitudes of the acoustic phonons are suppressed by tuning the small polarons absorption. This shows a coupled relationship between the acoustic phonons and the small polarons. At the probe photon energy of 1.55 eV where the polaron absorption is dominant, the acoustic phonons become unobservable. Furthermore, by performing the pump fluence dependent measurements on the LSMO films with different thicknesses, smaller acoustic phonon amplitudes are found in the thinner film with stronger small polaron binding energy. Such a coupled nature can be utilized to manipulate the small polarons using the acoustic phonons or vice versa, which is of great importance in device applications of colossal magnetoresistance materials

Ultrafast Orbital-Oriented Control of Magnetization in Half-Metallic La0.7Sr0.3MnO3 Films

Manipulating spins by ultrafast pulse laser provides a new avenue to switch the magnetization for spintronic applications. While the spin–orbit coupling is known to play a pivotal role in the ultrafast laser-induced demagnetization, the effect of the anisotropic spin–orbit coupling on the transient magnetization remains an open issue. This study uncovers the role of anisotropic spin–orbit coupling in the spin dynamics in a half-metallic La0.7Sr0.3MnO3 film by ultrafast pump–probe technique. The magnetic order is found to be transiently enhanced or attenuated within the initial sub-picosecond when the probe light is tuned to be s- or p-polarized, respectively. The subsequent slow demagnetization amplitude follows the fourfold symmetry of the dx2 y2 orbitals as a function of the polarization angles of the probe light. A model based on the Elliott–Yafet spin-flip scatterings is proposed to reveal that the transient magnetization enhancement is related to the spin-mixed states arising from the anisotropic spin–orbit coupling. The findings provide new insights into the spin dynamics in magnetic systems with anisotropic spin–orbit coupling as well as perspectives for the ultrafast control of information process in spintronic devices

Mechanisms by Which Physical Activity Modulates the Wnt/β-catenin Pathway to Alleviate Anxiety-like Depression

This study aimed to explore the effect of treadmill exercise on anxiety in rats. Thirty SPF male rats aged 2 months with a body mass of (225±25) g were randomly divided into control group (CG, n=10), chronic sleep deprivation group (CSD, n=10) and sleep deprivation exercise group (CSD+E, n=10) after adaptive feeding for 1 week. The CSD model of rats in CSD group and CSD+E group was made by multi platform water environment method. Sleep deprivation of 18 h per day (from 12:00 pm. to 6:00 am. the next day) for 8 weeks. The effect of running on the anxiety-like behaviour of CSD rats was examined in the open field test (OFT) and the elevated plus maze (EPM) experiment. Hematoxylin-eosin (HE) staining, Annexin V/PI flow cytometry, immunofluorescence staining, Western blot, RT-qPCR and other methods were used to detect the effects of treadmill exercise on the morphology of hippocampus, apoptosis related factors caspase-12, Bax, Bcl-1, inflammatory factors (IL-6, TNF-a), Wnt β- catenin, p- β-catenin. The results of HE staining showed that the brain tissue of the control rats was structurally intact, with thick layers of cone cells, relatively dense, neatly arranged and compact, the cell edge structures were intact and clearly visible, with no obvious abnormal changes. The cone cell layer of brain tissue in the chronic sleep deprivation group was thin, with relatively low cell density, disorganized and sparse arrangement, and blurred cell edges. The symptoms of the above pathological changes in brain tissue of rats in sleep deprivation exercise group gradually alleviated. OFT results showed that compared with CG group, the number of activities in the central region of CSD group was significantly reduced (P<0.01), and the total distance of exercise was significantly shortened (P<0.01). EPM results showed that compared with CG group, OT and CE in CSD group decreased significantly (P<0.01). CCK-8 results showed that compared with CG group, the activity of neurons in CA1 area of hippocampus in CSD group was significantly decreased (P<0.01), while that in CSD+E group was significantly increased (P<0.01); Annexin V/PI flow cytometry results showed that compared with CG group, the apoptosis of neurons in CA1 area of hippocampus in CSD group increased (P<0.01), and that in CSD+E group decreased significantly (P<0.01);Western blot results showed that caspase-12, Bax, IL-6, IL-1β and TNF-a were highly expressed and Bcl-1 was lowly expressed in hippocampal tissues of rats in the CSD group compared with the CG group (P<0.01), Wnt, β-catenin and p-β-catenin were lowly expressed in hippocampal tissues of rats in the CSD group, and Gsk-3βprotein expression was significantly higher (p<0.01). The results of RT-qPCR showed that caspase-12 mRNA, Bax mRNA, IL-6 mRNA, TNF-a mRNA and IL-1β mRNA were highly expressed and Bcl-1 mRNA was lowly expressed in hippocampal tissues of rats in the CSD group compared with the CG group (P<0.01). Compared with the CG group, Wnt mRNA and β-catenin mRNA were significantly lowly expressed and Gsk-3βmRNA was significantly highly expressed in hippocampal tissue of CSD rats (P<0.01). Our findings indicated that 8 weeks of aerobic exercise significantly improved anxiety-like depression in CSD rats by increasing neuronal activity, inhibiting apoptosis, reducing the inflammatory response and activating the Wnt/β-catenin pathway

Anisotropic ultrafast spin/valley dynamics in WTe2 films

WTe2 Weyl semimetal hosts the natural broken inversion symmetry and strong spin orbit coupling, making it promising for exotic spin/valley dynamics within a picosecond timescale. Here, we unveil an anisotropic ultrafast spin/valley dynamics in centimeter-scale, single-crystalline Td-WTe2 films using a femtosecond pump-probe technique at room temperature. We observe a transient (~0.8 ps) intra-valley transition and a subsequent polarization duration (~5 ps) during the whole spin/valley relaxation process. Furthermore, the relaxation exhibits the remarkable anisotropy of approximately six-fold and two-fold symmetries due to the intrinsic anisotropy along the crystalline orientation and the extrinsic matrix element effect, respectively. Our results offer a prospect for the ultrafast manipulation of spin/valleytronics in topological quantum materials for dissipationless high-speed spin/valleytronic devices.Comment: 21 pages, 4 figure

Observation of an anisotropic ultrafast spin relaxation process in large-area WTe2films

Weyl semimetal Td-WTe2 hosts the natural broken inversion symmetry and strong spin-orbit coupling, which contains profound spin-related physics within a picosecond timescale. However, the comprehensive understanding of ultrafast spin behaviors in WTe2 is lacking due to its limited quality of large-scale films. Here, we report on an anisotropic ultrafast spin dynamics in highly oriented Td-WTe2 films using a femtosecond pump-probe technique at room temperature. A transient spin polarization-flip transition as fast as 0.8 ps is observed upon photoexcitation. The inversed spin is subsequently scattered by defects with a duration of about 5.9 ps. The whole relaxation process exhibits an intriguing dual anisotropy of sixfold and twofold symmetries, which stems from the energy band anisotropy of the WTe2 crystalline structure and the matrix element effect, respectively. Our work enriches the insights into the ultrafast opto-spintronics in topological Weyl semimetals

Predictors of HIV and Syphilis among Men Who Have Sex with Men in a Chinese Metropolitan City: Comparison of Risks among Students and Non-Students

Men who have sex with men (MSM) are at a substantial risk of HIV, given rising HIV prevalence in urban China. Adolescent and adult students often take HIV-related risk as part of sexual exploration. We compared the risks of HIV and syphilis infections and risky sexual behaviors between student and non-student among urban MSM.Respondent driven sampling approach was used to recruit men who were self-identified as MSM in Chongqing Metropolitan City in southwestern China in 2009. Each participant completed a computer-assisted self-interview which collected demographic and behavioral data, and provided blood specimens for HIV and syphilis testing. Multivariable logistic regression analyses identified predictors for HIV and syphilis infections while comparing student and non-student MSM.Among 503 MSM participants, 36.4% were students, of whom 84.2% were in college. The adjusted prevalence of HIV infection was 5.5% (95% confidence interval [CI]: 2.1%-10.2%) in students and 20.9% (95% CI: 13.7%-27.5%) in non-students; the adjusted prevalence of syphilis was 4.4% (95% CI: 0.7%-9.0%) in students and 7.9% (95% CI: 3.6%-12.9%) in non-students (P = 0.12). Two groups had similar risky sexual behaviors such as number of sexual partners and exchanging sex for money. Multivariate analysis showed that students had lower HIV prevalence than non-students (adjusted odds ratio [AOR]: 0.3; 95% CI: 0.1-0.8) adjusting for age, ethnicity and other variables.Student MSM have lower HIV and similar syphilis prevalence compared with non-student MSM. However, due to a shorter duration of sexual experience and high prevalence of at-risk sexual behaviors among student MSM, HIV risk might be quite high in students as in non-students

Impurity band assisted carrier relaxation in Cr doped topological insulator Bi2Se3

Topological insulators (TIs) with unique band structures have wide application prospects in the fields of ultrafast optical and spintronic devices. The dynamics of hot carriers plays a key role in these TI-based devices. In this work, using the time- and angle-resolved photoemission spectroscopy technique, the relaxation process of the hot carriers in Cr-doped Bi2Se3 has been systematically studied since the ferromagnetic TI is one of the key building blocks for next-generation spintronics. It is found that electronic temperature (Te) and chemical potential (μ) decrease faster with the increase in the Cr doping concentration. Similarly, the lifetime (τ) of the excited electrons also decreases with more Cr doped into Bi2Se3. The results suggest a mechanism of impurity band-assisted carrier relaxation, where the impurity band within the bulk bandgap introduced by Cr doping provides significant recombination channels for the excited electrons. This work directly illustrates the dynamic process of the photon-generated carriers in Cr-doped Bi2Se3, which is expected to promote the applications of (Bi1-xCrx)2Se3 in photoelectric devices

Stimulation of Midbrain Dopaminergic Structures Modifies Firing Rates of Rat Lateral Habenula Neurons

Ventral tegmental area (VTA) and substantia nigra pars compacta (SNpc) are midbrain structures known to be involved in mediating reward in rodents. Lateral habenula (LHb) is considered as a negative reward source and it is reported that stimulation of the LHb rapidly induces inhibition of firing in midbrain dopamine neurons. Interestingly, the phasic fall in LHb neuronal activity may follow the excitation of dopamine neurons in response to reward-predicting stimuli. The VTA and SNpc give rise to dopaminergic projections that innervate the LHb, which is also known to be involved in processing painful stimuli. But it's unclear what physiological effects these inputs have on habenular function. In this study we distinguished the LHb pain-activated neurons of the Wistar rats and assessed their electrophysiological responsiveness to the stimulation of the VTA and SNpc with either single-pulse stimulation (300 µA, 0.5 Hz) or tetanic stimulation (80 µA, 25 Hz). Single-pulse stimulation that was delivered to either midbrain structure triggered transient inhibition of firing of ∼90% of the LHb pain-activated neurons. However, tetanic stimulation of the VTA tended to evoke an elevation in neuronal firing rate. We conclude that LHb pain-activated neurons can receive diverse reward-related signals originating from midbrain dopaminergic structures, and thus participate in the regulation of the brain reward system via both positive and negative feedback mechanisms

Spin-ARPES EUV beamline for ultrafast materials research and development

A new femtosecond, Extreme Ultraviolet (EUV), Time Resolved Spin-Angle Resolved Photo-Emission Spectroscopy (TR-Spin-ARPES) beamline was developed for ultrafast materials research and development. This 50-fs laser-driven, table-top beamline is an integral part of the "Ultrafast Spintronic Materials Facility", dedicated to engineering ultrafast materials. This facility provides a fast and in-situ analysis and development of new materials. The EUV source based on high harmonic generation process emits 2.3 × 1011 photons/second (2.3 × 108 photons/pulse) at H23 (35.7 eV) and its photon energy ranges from 10 eV to 75 eV, which enables surface sensitive studies of the electronic structure dynamics. The EUV monochromator provides the narrow bandwidth of the EUV beamline while preserving its pulse duration in an energy range of 10-100 eV. Ultrafast surface photovoltaic effect with ~650 fs rise-time was observed in p-GaAs (100) from time-resolved ARPES spectra. The data acquisition time could be reduced by over two orders of magnitude by scaling the laser driver from 1 KHz, 4W to MHz, KW average power