1,224 research outputs found
Gluon scattering in AdS at finite string coupling from localization
We consider gluons scattering in Type IIB string theory on AdS in the presence of D7 branes, which is dual to the flavor
multiplet correlator in a certain 4d gauge theory
with flavor symmetry and complexified coupling . We compute this
holographic correlator in the large and finite expansion using
constraints from derivatives of the mass deformed sphere free energy, which we
compute to all orders in and finite using supersymmetric
localization. In particular, we fix the higher derivative correction to
gluon scattering on AdS at finite string coupling in terms of
Jacobi theta functions, which feature the expected relations between the
duality and the triality of the CFT, and match it to
the known flat space term. We also use the flat space limit to compute
corrections of the correlator at finite in terms of a non-holomorphic
Eisenstein series. At weak string coupling, we find that the AdS correlator
takes a form which is remarkably similar to that of the flat space Veneziano
amplitude.Comment: 24 pages plus appendice
Carrier-induced ferromagnetism in n-type ZnMnAlO and ZnCoAlO thin films at room temperature
The realization of semiconductors that are ferromagnetic above room
temperature will potentially lead to a new generation of spintronic devices
with revolutionary electrical and optical properties. Transition temperatures
in doped ZnO are high but, particularly for Mn doping, the reported moments
have been small. We show that by careful control of both oxygen deficiency and
aluminium doping the ferromagnetic moments measured at room temperature in
n-type ZnMnO and ZnCoO are close to the ideal values of 5mB and 3mB
respectively. Furthermore a clear correlation between the magnetisation per
transition metal ion and the ratio of the number of carriers to the number of
transition metal donors was established as is expected for carrier induced
ferromagnetism for both the Mn and Co doped films. The dependence of the
magnetisation on carrier density is similar to that predicted for the
transition temperature for a dilute magnetic semiconductor in which the
exchange between the transition metal ions is through the free carriers.Comment: 14 pages pd
Into the Absolute: Recent Paintings by James M. Behan Show Card
Show card for Into the Absolute: Recent Paintings by James M. Behan. February 5 - February 19, 1990.https://digitalcommons.udallas.edu/absolute_behan/1000/thumbnail.jp
Help-seeking behaviors and mental well-being of first year undergraduate university students
University students demonstrate poor help-seeking behaviors for their mental health, despite often reporting low levels of mental well-being. The aims of this study were to examine the help-seeking intentions and experiences of first year university students in terms of their mental well-being, and to explore these students’ views on formal (e.g. psychiatrists) and informal (e.g. friends) help-seeking. Students from a university in the Republic of Ireland (n=220) completed an online questionnaire which focused on mental well-being and help-seeking behaviors. Almost a third of students had sought help from a mental health professional. Very few students reported availing of university/online supports. Informal sources of help were more popular than formal sources, and those who would avail and had availed of informal sources demonstrated higher well-being scores. Counselors were the source of professional help most widely used. General practitioners, chaplains, social workers, and family therapists were rated the most helpful. Those with low/average well-being scores were less likely to seek help than those with higher scores. Findings indicate the importance of enhancing public knowledge of mental health issues, and for further examination of students’ knowledge of help-seeking resources in order to improve the help-seeking behaviors and mental well-being of this population group
Spin polarized transport current in n-type co-doped ZnO thin films measured by Andreev spectroscopy
We use point contact Andreev reflection measurements to determine the spin
polarization of the transport current in pulse laser deposited thin films of
ZnO with 1% Al and with and without 2%Mn. Only films with Mn are ferromagnetic
and show spin polarization of the transport current of up to 55 0.5% at
4.2 K, in sharp contrast to measurements of the nonmagnetic films without Mn
where the polarization is consistent with zero. Our results imply strongly that
ferromagnetism in these Al doped ZnO films requires the presence of Mn.Comment: Published versio
Alpha-linolenic acid supplementation in Tris extender can improve frozen–thawed bull semen quality
The study was conducted to evaluate the effects of α-linolenic acid (ALA) on frozen–thawed quality and fatty acid composition of bull sperm. For that, twenty-four ejaculates obtained from three bulls were diluted in a Tris extender containing 0 (control), 3, 5, 10 and 15 ng/ml of ALA. Extended semen was incubated at 37°C for 15 min, to allow absorption of ALA by sperm cell membrane. The sample was chilled for 2 h, packed into 0.25-ml straws and frozen in liquid nitrogen for 24 h. Subsequently, straws were thawed and evaluated for total sperm motility (computer-assisted semen analysis), membrane functional integrity (hypo-osmotic swelling test), viability (eosin-nigrosin), fatty acid composition (gas chromatography) and lipid peroxidation (thiobarbituric acid-reactive substances (TBARS)). A higher (p < 0.05) percentage of total sperm motility was observed in ALA groups 5 ng/ml (47.74 ± 07) and 10 ng/ml (44.90 ± 0.7) in comparison with control (34.53 ± 3.0), 3 ng/ml (34.40 ± 2.6) and 15 ng/ml (34.60 ± 2.9). Still, the 5 ng/ml ALA group presented a higher (p < 0.05) percentage of viable sperms (74.13 ± 0.8) and sperms with intact membrane (74.46 ± 09) than all other experimental groups. ALA concentration and lipid peroxidation in post-thawed sperm was higher in all treated groups when compared to the control group. As such, the addition of 5 ng/ml of ALA to Tris extender improved quality of frozen–thawed bull spermatozoa
On the feasibility of N2 fixation via a single-site FeI/FeIV cycle: Spectroscopic studies of FeI(N2)FeI, FeIV=N, and related species
The electronic properties of an unusually redox-rich iron system, [PhBPR 3]FeNx (where [PhBPR 3] is [PhB(CH2PR2)3]−), are explored by Mössbauer, EPR, magnetization, and density-functional methods to gain a detailed picture regarding their oxidation states and electronic structures. The complexes of primary interest in this article are the two terminal iron(IV) nitride species, [PhBPiPr 3]FeN (3a) and [PhBPCH2Cy 3]FeN (3b), and the formally diiron(I) bridged-Fe(μ-N2)Fe species, {[PhBPiPr 3]Fe}2(μ-N2) (4). Complex 4 is chemically related to 3a via a spontaneous nitride coupling reaction. The diamagnetic iron(IV) nitrides 3a and 3b exhibit unique electronic environments that are reflected in their unusual Mössbauer parameters, including quadrupole-splitting values of 6.01(1) mm/s and isomer shift values of −0.34(1) mm/s. The data for 4 suggest that this complex can be described by a weak ferromagnetic interaction (J/D < 1) between two iron(I) centers. For comparison, four other relevant complexes also are characterized: a diamagnetic iron(IV) trihydride [PhBPiPr 3]Fe(H)3(PMe3) (5), an S = 3/2 iron(I) phosphine adduct [PhBPiPr 3]FePMe3 (6), and the S = 2 iron(II) precursors to 3a, [PhBPiPr 3]FeCl and [PhBPiPr 3]Fe-2,3:5,6-dibenzo-7-aza bicyclo[2.2.1]hepta-2,5-diene (dbabh). The electronic properties of these respective complexes also have been explored by density-functional methods to help corroborate our spectral assignments and to probe their electronic structures further
Room temperature magneto-optics of ferromagnetic transition-metal doped ZnO thin films
Magneto-optic studies of ZnO doped with transition metals Co, Mn, V and Ti
indicate a significant magnetic circular dichroism (MCD) at the ZnO band edge
at room temperature, together with an associated dispersive Faraday rotation.
Similar spectra occur for each dopant which implies that the ferromagnetism is
an intrinsic property of the bulk ZnO lattice. At 10 K additional paramagnetic
contributions to the MCD are observed, but above about 150K, the magnitude of
the MCD signal is dominated by the ferromagnetism and is almost temperature
independent. The MCD at the ZnO band edge shows room temperature hysteretic
behaviour.Comment: 4 page
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