Supersymmetry breaking,heterotic strings and fluxes

In this paper we consider compactifications of heterotic strings in the presence of background flux. The background metric is a T² fibration over a K3 base times four-dimensional Minkowski space. Depending on the choice of three-form flux different amounts of supersymmetry are preserved (N=2,1,0$N=2,1,0$). For supersymmetric solutions unbroken space–time supersymmetry determines all background fields except one scalar function which is related to the dilaton. The heterotic Bianchi identity gives rise to a differential equation for the dilaton which we discuss in detail for solutions preserving an N=2$N=2$ supersymmetry. In this case the differential equation is of Laplace type and as a result the solvability is guaranteed.     

Synthesis and circular dichroism studies of steroidal schiff bases of biogenic amines

A number of imines (Schiff bases) have been prepared from ketosteroids (estrone, estrone-3-methyl ether, androsterone, epiandrosterone, 5α-cholestan-3-one, 6-ketocholestanol and testosterone) and primary amines (phenethylamine, tyramine and hexanamine). The CD spectra of these compounds have been measured in methanol. Except for the testosterone imines, the azomethine n-π^* band (~ 235 nm) exhibited the same sign (but not as high an ellipticity) as the parent ketone's n - π^* band (~295 nm). The imines of the estrogens (estrone and estrone 3-methyl ether) gave CD spectra characterized by a negative ¹L_b Cotton effect ([θ] ? -1000) near 280 nm and a band near 230 nm ([θ] ? +19,000) which is considered the sum of a positive azomethine n - π^* Cotton effect and positive aromatic ¹L_a Cotton effect(s). The ¹L_a band originating in the amine moiety was prominent in the CD of 5α-cholestan-3-one and 6-ketocholestanol phenethylamine imines. When aromatic Cotton effects originating in the amine moiety were detected, they were of the same sign as the n - π^* Cotton effect.     

Tri-partite complex for axonal transport drug delivery achieves pharmacological effect

Background

Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System) neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior.

Results

We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle.

Conclusion

Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal transport holds great promise. The data shown here provide a basic framework for the intraneural pharmacology of this tripartite complex. The pharmacologically efficacious drug delivery demonstrated here verify the fundamental feasibility of using axonal transport for targeted drug delivery.     

色谱研究的最新进展

作为本期《色谱》的聚焦专栏评述,笔者主要介绍国内外学者在2010年3月和4月间发表的一些研究工作［1-9］,内容集中在色谱研究和应用的两个方面:新型色谱材料和方法技术的开发［1－5］;色谱在蛋白质组学分析中的新应用［6,7］。另外,近期也有不少关于微流控分析应用的具有特色的工作［8］,由于篇幅限制就不在这里详细介绍。     

Monodromy groups of Hurwitz-type problems

We solve the Hurwitz monodromy problem for degree 4 covers. That is, the Hurwitz space H4,g of all simply branched covers of P¹ of degree 4 and genus g is an unramified cover of the space P2g+6 of (2g+6)-tuples of distinct points in P¹. We determine the monodromy of π₁(P2g+6) on the points of the fiber. This turns out to be the same problem as the action of π₁(P2g+6) on a certain local system of Z/2-vector spaces. We generalize our result by treating the analogous local system with Z/N coefficients, 3?N, in place of Z/2. This in turn allows us to answer a question of Ellenberg concerning families of Galois covers of P¹ with deck group ²(Z/N):S₃.     

Variance Bounding of Delayed-Acceptance Kernels

Methodology and Computing in Applied Probability - A delayed-acceptance version of a Metropolis–Hastings algorithm can be useful for Bayesian inference when it is computationally expensive to...     

Mechanistic Insight into Energy-Transfer Dynamics and Color Tunability of Na4CaSi3O9:Tb3+,Eu3+ for Warm White LEDs

In this work, a latent energy-transfer process in traditional Eu³⁺,Tb³⁺-doped phosphors is proposed and a new class of Eu³⁺,Tb³⁺-doped Na₄CaSi₃O₉ (NCSO) phosphors is presented which is enabled by luminescence decay dynamics that optimize the electron-transfer energy process. Relative to other Eu³⁺,Tb³⁺-doped phosphors, the as-synthesized Eu³⁺,Tb³⁺-doped NCSO phosphors show improved large-scale tunable emission color from green to red upon UV excitation, controlled by the Tb³⁺/Eu³⁺ doping ratio. Detailed spectroscopic measurements in the vacuum ultraviolet (VUV)/UV/Vis region were used to determine the Eu³⁺–O²⁻ charge-transfer energy, 4f–5d transition energies, and the energies of 4f excited multiplets of Eu³⁺ and Tb³⁺ with different 4f^N electronic configurations. The Tb³⁺→Eu³⁺ energy-transfer pathway in the co-doped sample was systematically investigated, by employing luminescence decay dynamics analysis to elucidate the relevant energy-transfer mechanism in combination with the appropriate model simulation. To demonstrate their application potential, a prototype white-light-emitting diode (WLED) device was successfully fabricated by using the yellow luminescence NCSO:0.03Tb³⁺, 0.05Eu³⁺ phosphor with high thermal stability and a BaMgAl₁₀O₁₇:Eu²⁺ phosphor in combination with a near-UV chip. These findings open up a new avenue to realize and develop multifunctional high-performance phosphors by manipulating the energy-transfer process for practical applications.     

Leveraging the design heuristics of realistic mathematics education and culturally responsive pedagogy to create a richer flipped classroom calculus curriculum

ZDM – Mathematics Education - While the number of studies of flipped classrooms has increased, they have primarily addressed the efficacy of using such an approach on student outcomes, often...     

Error bounds in the gap metric for dissipative balanced approximations

We derive an error bound in the gap metric for positive real balanced truncation and positive real singular perturbation approximation. We prove these results by working in the context of dissipative driving-variable systems, as in behavioral and state/signal systems theory. In such a framework no prior distinction is made between inputs and outputs. Dissipativity preserving balanced truncation of dissipative driving-variable systems is addressed and a gap metric error bound is obtained. Bounded real and positive real input–state–output systems are manifestations of a dissipative driving-variable system through particular decompositions of the signal space. Under such decompositions the existing bounded real and positive real balanced truncation schemes can be seen as special cases of dissipative balanced truncation and the new positive real error bounds follow.