Inhibition of DNA ejection from bacteriophage by Mg+2 counterions

The problem of inhibiting viral DNA ejection from bacteriophages by multivalent counterions, specifically Mg$^{+2}$ counterions, is studied. Experimentally, it is known that MgSO$_4$ salt has a strong and non-monotonic effect on the amount of DNA ejected. There exists an optimal concentration at which the minimum amount of DNA is ejected from the virus. At lower or higher concentrations, more DNA is ejected from the capsid. We propose that this phenomenon is the result of DNA overcharging by Mg$^{+2}$ multivalent counterions. As Mg$^{+2}$ concentration increases from zero, the net charge of DNA changes from negative to positive. The optimal inhibition corresponds to the Mg$^{+2}$ concentration where DNA is neutral. At lower/higher concentrations, DNA genome is charged. It prefers to be in solution to lower its electrostatic self-energy, which consequently leads to an increase in DNA ejection. By fitting our theory to available experimental data, the strength of DNA$-$DNA short range attraction energies, mediated by Mg$^{+2}$, is found to be $-$0.004 $k_BT$ per nucleotide base. This and other fitted parameters agree well with known values from other experiments and computer simulations. The parameters are also in aggreement qualitatively with values for tri- and tetra-valent counterions.Comment: 17 pages, 4 figures, improved manuscript. Submitted to J. Chem. Phys (2010

T1T_1- and T2T_2-spin relaxation time limitations of phosphorous donor electrons near crystalline silicon to silicon dioxide interface defects

A study of donor electron spins and spin--dependent electronic transitions involving phosphorous ($^{31}$P) atoms in proximity of the (111) oriented crystalline silicon (c-Si) to silicon dioxide (SiO$_{2}$) interface is presented for [$^{31}$P] = 10$^{15}$ $\mathrm{cm}^{-3}$ and [$^{31}$P] = 10$^{16}$ $\mathrm{cm}^{-3}$ at about liquid $^4$He temperatures ($T = 5$ $\mathrm{K} - 15$ $\mathrm{K}$). Using pulsed electrically detected magnetic resonance (pEDMR), spin--dependent transitions between the \Phos donor state and two distinguishable interface states are observed, namely (i) \Pb centers which can be identified by their characteristic anisotropy and (ii) a more isotropic center which is attributed to E$^\prime$ defects of the \sio bulk close to the interface. Correlation measurements of the dynamics of spin--dependent recombination confirm that previously proposed transitions between \Phos and the interface defects take place. The influence of these electronic near--interface transitions on the \Phos donor spin coherence time $T_2$ as well as the donor spin--lattice relaxation time $T_1$ is then investigated by comparison of spin Hahn--echo decay measurements obtained from conventional bulk sensitive pulsed electron paramagnetic resonance and surface sensitive pEDMR, as well as surface sensitive electrically detected inversion recovery experiments. The measurements reveal that both $T_2$ and $T_1$ of \Phos donor electrons spins in proximity of energetically lower interface states at $T\leq 13$ K are reduced by several orders of magnitude

Antiferromagnetic Order in MnO Spherical Nanoparticles

We have performed unpolarized and polarized neutron diffraction experiments on monodisperse 8 nm and 13 nm antiferromagnetic MnO nanoparticles. For the 8 nm sample, the antiferromagnetic transition temperature $T_N$ (114 K) is suppressed compared to the bulk material (119 K) while for the 13 nm sample $T_N$ (120 K) is comparable to the bulk. The neutron diffraction data of the nanoparticles is well described using the bulk MnO magnetic structure but with a substantially reduced average magnetic moment of 4.2$\pm$0.3 $\mu_B$/Mn for the 8 nm sample and 3.9$\pm$0.2 $\mu_B$/Mn for the 13 nm sample. An analysis of the polarized neutron data on both samples shows that in an individual MnO nanoparticle about 80$$ of Mn ions order. These results can be explained by a structure in which the monodisperse nanoparticles studied here have a core that behaves similar to the bulk with a surface layer which does not contribute significantly to the magnetic order.Comment: 7 pages, 5 figure

The Commoditization of IT: Evidence from a Longitudinal Text Mining Study

While Information Technology (IT) has been identified by researchers as a source of strategic advantage for businesses, commentators have argued that this reality may not endure. These commentators argue that the growing ubiquity of IT makes it a commodity input rather than a scarce and valuable resource. We examine CEOs’ Letters to Shareholders, one of the primary statements of corporate strategy, using both content analysis and latent semantic analysis, a text mining technique. Examining these letters allows us to investigate whether IT may be declining in strategic importance over time. We examine 160 annual reports from firms in the healthcare industry, covering a ten-year span of time, from 1997 through 2006. Our results indicate that the strategic emphasis placed on IT may be increasing, but its association with firm performance is declining. Our findings imply that as markets become more competitive, IT management capabilities and the strategic use of IT take on increasing importance. Our findings also imply that CEOs’ perception of the importance of IT is a necessary but not a sufficient condition for improved firm performance. This article makes two primary contributions. First, we present an empirical examination of the issue of IT commoditization as a complement to existing anecdotal discussions. Second, we demonstrate the use of latent semantic analysis (LSA), a relatively new methodology for analyzing textual data, one that is evolving into an alternative to the well-known content analysis technique

Time dependent transformations in deformation quantization

We study the action of time dependent canonical and coordinate transformations in phase space quantum mechanics. We extend the covariant formulation of the theory by providing a formalism that is fully invariant under both standard and time dependent coordinate transformations. This result considerably enlarges the set of possible phase space representations of quantum mechanics and makes it possible to construct a causal representation for the distributional sector of Wigner quantum mechanics.Comment: 16 pages, to appear in the J. Math. Phy

Comprehensive Solution to the Cosmological Constant, Zero-Point Energy, and Quantum Gravity Problems

We present a solution to the cosmological constant, the zero-point energy, and the quantum gravity problems within a single comprehensive framework. We show that in quantum theories of gravity in which the zero-point energy density of the gravitational field is well-defined, the cosmological constant and zero-point energy problems solve each other by mutual cancellation between the cosmological constant and the matter and gravitational field zero-point energy densities. Because of this cancellation, regulation of the matter field zero-point energy density is not needed, and thus does not cause any trace anomaly to arise. We exhibit our results in two theories of gravity that are well-defined quantum-mechanically. Both of these theories are locally conformal invariant, quantum Einstein gravity in two dimensions and Weyl-tensor-based quantum conformal gravity in four dimensions (a fourth-order derivative quantum theory of the type that Bender and Mannheim have recently shown to be ghost-free and unitary). Central to our approach is the requirement that any and all departures of the geometry from Minkowski are to be brought about by quantum mechanics alone. Consequently, there have to be no fundamental classical fields, and all mass scales have to be generated by dynamical condensates. In such a situation the trace of the matter field energy-momentum tensor is zero, a constraint that obliges its cosmological constant and zero-point contributions to cancel each other identically, no matter how large they might be. Quantization of the gravitational field is caused by its coupling to quantized matter fields, with the gravitational field not needing any independent quantization of its own. With there being no a priori classical curvature, one does not have to make it compatible with quantization.Comment: Final version, to appear in General Relativity and Gravitation (the final publication is available at http://www.springerlink.com). 58 pages, revtex4, some additions to text and some added reference

Generalized Weyl-Wigner map and Vey quantum mechanics

The Weyl-Wigner map yields the entire structure of Moyal quantum mechanics directly from the standard operator formulation. The covariant generalization of Moyal theory, also known as Vey quantum mechanics, was presented in the literature many years ago. However, a derivation of the formalism directly from standard operator quantum mechanics, clarifying the relation between the two formulations is still missing. In this paper we present a covariant generalization of the Weyl order prescription and of the Weyl-Wigner map and use them to derive Vey quantum mechanics directly from the standard operator formulation. The procedure displays some interesting features: it yields all the key ingredients and provides a more straightforward interpretation of the Vey theory including a direct implementation of unitary operator transformations as phase space coordinate transformations in the Vey idiom. These features are illustrated through a simple example.Comment: 15 pages, LaTe

Novel health systems service design checklist to improve healthcare access for marginalised, underserved communities in Europe.

BACKGROUND content: Marginalised communities such as homeless people, people who use drugs (PWUD), lesbian, gay, bisexual, transgender and intersex people (LGBTI), prisoners, sex workers and undocumented migrants are at high risk of poor health and yet face substantial barriers in accessing health and support services. The Nobody Left Outside (NLO) Service Design Checklist aims to promote a collaborative, evidence-based approach to service design and monitoring based on equity, non-discrimination and community engagement. METHODS content: The Checklist was a collaborative project involving nine community advocacy organisations, with a focus on homeless people, PWUD, LGBTI people, prisoners, sex workers, and undocumented migrants. The Checklist was devised via a literature review; two NLO platform meetings; a multistakeholder policy workshop and an associated published concept paper; two conference presentations; and stakeholder consultation via a European Commission-led Thematic Network (including webinar). RESULTS content: "The NLO Checklist has six sections in line with the WHO Health Systems Framework. These are: (1) service delivery, comprising design stage (6 items), services provided (2 items), accessibility and adaptation (16 items), peer support (2 items); (2) health workforce (12 items); (3) health information systems (7 items); (4) medical products and technologies (1 item); (5) financing (3 items); and (6) leadership and governance (7 items). It promotes the implementation of integrated (colocated or linked) healthcare services that are community based and people centred. These should provide a continuum of needs-based health promotion, disease prevention, diagnosis, treatment and management, together with housing, legal and social support services, in alignment with the goals of universal health coverage and the WHO frameworks on integrated, people-centred healthcare."CONCLUSIONS content: The Checklist is offered as a practical tool to help overcome inequalities in access to health and support services. Policymakers, public health bodies, healthcare authorities, practitioner bodies, peer support workers and non-governmental organisations can use it when developing, updating or monitoring services for target groups. It may also assist civil society in wider advocacy efforts to improve access for underserved communities

Cerebral Small Vessel Disease: Cognition, Mood, Daily Functioning, and Imaging Findings from a Small Pilot Sample

Cerebral small vessel disease, a leading cause of cognitive decline, is considered a relatively homogeneous disease process, and it can co-occur with Alzheimer's disease. Clinical reports of magnetic resonance imaging (MRI)/computed tomography and single photon emission computed tomography (SPECT) imaging and neuropsychology testing for a small pilot sample of 14 patients are presented to illustrate disease characteristics through findings from structural and functional imaging and cognitive assessment. Participants showed some decreases in executive functioning, attention, processing speed, and memory retrieval, consistent with previous literature. An older subgroup showed lower age-corrected scores at a single time point compared to younger participants. Performance on a computer-administered cognitive measure showed a slight overall decline over a period of 8–28 months. For a case study with mild neuropsychology findings, the MRI report was normal while the SPECT report identified perfusion abnormalities. Future research can test whether advances in imaging analysis allow for identification of cerebral small vessel disease before changes are detected in cognition