Absolute photoionization cross sections of atomic oxygen

The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states

Sperm DNA damage in relation to lipid peroxidation following freezing-thawing of boar semen

This study investigated the relationships between lipid peroxidation (LPO) and sperm DNA damage following freezing-thawing of boar semen in different extenders. The comet assay was used to measure the extent of sperm DNA damage in a cryoprotectant-free extender or in cryoprotectant-based extenders after single and repeated freezing and thawing. As well as an analysis of sperm motion characteristics, mitochondrial function, membrane integrity, and lipid peroxidation (LPO) were assessed simultaneously with the measurements of sperm DNA damage. Consistent positive significant correlations were found between sperm DNA damage and LPO after freezing-thawing. Comet assay measurements showed that cryo-induced sperm DNA damage was more marked in the cryoprotectant-free extender, irrespective of freezing cycle. The frequency of sperm cells with damaged DNA increased with repeated freezing and thawing in the cryoprotectant-based extenders. Except for sperm DNA damage, there were no consistent associations between post-thaw sperm LPO and sperm quality characteristics. It could be suggested that the increased LPO of membrane phospholipids is associated with higher susceptibility of boar spermatozoa to cryo-induced DNA damage.Keywords: Comet assay measurements, cryopreservation, extenders, spermatozo

Treating latent TB in primary care: a survey of enablers and barriers among UK General Practitioners.

BACKGROUND: Treating latent tuberculosis infection (LTBI) is an important public health intervention. In the UK, LTBI treatment is delivered in secondary care. Treating LTBI in the community would move care closer to home and could increase uptake and treatment completion rates. However, healthcare providers' views about the feasibility of this in the UK are unknown. This is the first study to investigate perceived barriers and enablers to primary care-based LTBI treatment among UK general practitioners (GPs). METHODS: A national survey amongst 140 randomly sampled UK GPs practising in areas of high TB incidence was performed. GPs' experience and perceived confidence, barriers and enablers of primary care-based LTBI treatment were explored and multivariable logistic regression was used to determine whether these were associated with a GP's willingness to deliver LTBI treatment. RESULTS: One hundred and twelve (80 %) GPs responded. Ninety-three (83 %; 95 % CI 75 %-89 %) GPs said they would be willing to deliver LTBI treatment in primary care, if key perceived barriers were addressed during service development. The major perceived barriers to delivering primary care-based LTBI treatment were insufficient experience among GPs of screening and treating LTBI, lack of timely specialist support and lack of allied healthcare staff. In addition, GPs felt that appropriate resourcing was key to the successful and sustainable delivery of the service. GPs who reported previous experience of screening or treatment of patients with active or latent TB were almost ten times more likely to be willing to deliver LTBI treatment in primary care compared to GPs with no experience (OR: 9.98; 95 % CI 1.22-81.51). CONCLUSIONS: UK GPs support primary care-based LTBI treatment, provided they are given appropriate training, specialist support, staffing and financing

Panel: COVID-19 Challenges to Project Management

COVID-19 has presented many new challenges and new opportunities for project management professionals and IT leaders. This panel will address these challenges and identify project management best practices and processes which have been effective in meeting these challenges. The panelists will share specific instances and challenges explaining how Project Cost Management, Time Management, Risk Management, Human Resources Management, and Risk Management have enabled them to manage during the pandemic and as a part of “return-to-work” scenarios. Hearing from these leaders as they accomplish digital transformations for their businesses and organizations will be an opportunity to bridge the gap between research and practice and to establish a dialogue between academic leaders and IT industry leaders which will provide many new questions to come

Bubbles in viscous liquids: Time dependent behaviour and wake characteristics

The dynamics of a bubble, initially stationary and spherical, rising in a viscous Newtonian liquid have been studied numerically using 3-D Volume-of-Fluid (VOF) method implemented in the Gerris flow solver. The study encompasses 8.7≤Eo (=ΔρgD2/σΔρgD2/σ)≤641 and Re≤151. Additionally, results published in the literature encompassing bubbles with lower values of Eo numbers were also considered, such that the overall dependencies of bubble shape, wake characteristics, and drag coefficient over a large range of Eo and Re values can be identified. While it was found that the deformation of the bubbles as predicted through the numerical study can generally replicate experimental observations presented, several limitations were identified, such as in the representation of skirt formation behind a skirted bubble and the formation of satellite bubbles behind a bubble rising at high Reynolds numbers. The dependency of the bubble aspect ratio on the Weber and Morton numbers was confirmed for cases of spherical and ellipsoidal bubbles; whilst for spherical cap and skirted bubbles the aspect ratio was found to depend largely on the Reynolds and Capillary numbers, respectively. Finally, the expansion and formation of closed/open laminar wakes behind the rising bubble were analysed and was found to correlate well with the bubble Re and Eo numbers

Comparison between the two models of dephasing in mesoscopic systems

In mesoscopic systems to study the role of inelastic scattering on the phase coherent motion of electrons two phenomenological models have been proposed. In the first one, due to B\"uttiker, one adds a voltage probe into the system (or in the scattering matrix). The second model invokes the complex (or optical) potential in the system Hamiltonian. Studying a simple geometry of a metallic loop in the presence of Aharonov-Bohm magnetic flux, we show that the two probe conductance is symmetric in the reversal of the magnetic field in B\"uttiker's approach. Whereas the two probe conductance within the complex potential model is asymmetric in the magnetic flux reversal contrary to the expected behavior.Comment: 11 pages RevTex, 4 figures inculded, Communicated to PR

Aharonov-Bohm oscillations and spin transport in a mesoscopic ring with a magnetic impurity

We present a detailed analysis of the Aharonov-Bohm (AB) interference oscillations manifested through transmission of an electron in a mesoscopic ring with a magnetic impurity atom inserted in one of its arms. The spin polarization transport is also studied. The electron interacts with the impurity through the exchange interaction leading to exchange spin-flip scattering. Transmission in the spin-flipped and spin-unflipped channels are explicitly calculated. We show that the entanglement between electron and spin-flipper states lead to a reduction of AB oscillations in spite of absence of any inelastic scattering. The spin-conductance (related to spin-polarized transmission coefficient) is asymmetric in the flux reversal as opposed to the two probe conductance which is symmetric under flux reversal. We point out certain limitations of this model in regard to the general notion of dephasing in quantum mechanics.Comment: 6 pages RevTeX, 9 eps figures included, enlarged version of cond-mat/000741

Carrier induced ferromagnetism in diluted magnetic semi-conductors

We present a theory for carrier induced ferromagnetism in diluted magnetic semi-conductor (DMS). Our approach treats on equal footing quantum fluctuations within the RPA approximation and disorder within CPA. This method allows for the calculation of $T_c$, magnetization and magnon spectrum as a function of hole, impurity concentration and temperature. It is shown that, sufficiently close to $T_c$, and within our decoupling scheme (Tyablicov type) the CPA for the itinerant electron gas reduces to the Virtual Crystal Approximation. This allows, in the low impurity concentration and low density of carriers to provide analytical expression for $T_c$. For illustration, we consider the case of $Ga_{1-c}Mn_{c}As$ and compare our results with available experimental data.Comment: 5 figures included. to appear in Phys. Rev. B (brief report

Spin Polarization at Semiconductor Point Contacts in Absence of Magnetic Field

Semiconductor point contacts can be a useful tool for producing spin-polarized currents in the presence of spin-orbit (SO) interaction. Neither magnetic fields nor magnetic materials are required. By numerical studies, we show that (i) the conductance is quantized in units of 2e^2/h unless the SO interaction is too strong, (ii) the current is spin-polarized in the transverse direction, and (iii) a spin polarization of more than 50% can be realized with experimentally accessible values of the SO interaction strength. The spin-polarization ratio is determined by the adiabaticity of the transition between subbands of different spins during the transport through the point contacts.Comment: 4 pages, 4 figures; minor changes, published in J. Phys. Soc. Jp