‘User-friendly’ primary phosphines and an arsine: synthesis and characterization of new air-stable ligands incorporating the ferrocenyl group

Reaction of FcCH₂CH₂P(O)(OH)₂ or FcCH₂P(O)(OH)(OEt) [Fc=Fe(η⁵-C₅H₄)(η⁵-C₅H₅)] with excess CH₂N₂ followed by reduction with Me₃SiCl–LiAlH₄ gives the air-stable primary phosphines FcCH₂CH₂PH₂ and the previously reported analogue FcCH₂PH₂ in high yields. Reduction of 1,1′-Fc′[CH₂P(O)(OEt)₂] [Fc′=Fe(η⁵-C₅H₄)₂] and 1,2-Fc″[CH₂P(O)(OEt)₂] [Fc″=Fe(η⁵-C₅H₅)(η⁵-C₅H₃)] similarly gives the new primary phosphines 1,1′-Fc′(CH₂PH₂)₂ and 1,2-Fc″(CH₂PH₂)₂, respectively. The arsine FcCH₂CH₂AsH₂, which is also air-stable, has been prepared by reduction of the arsonic acid FcCH₂CH₂As(O)(OH)₂ using Zn/HCl. An X-ray structure has been carried out on the arsine, which is only the second structure determination of a free primary arsine. The molybdenum carbonyl complex [1,2-Fc″(CH₂PH₂)₂Mo(CO)₄] was prepared by reaction of the phosphine with [Mo(CO)₄(pip)₂] (pip=piperidine), and characterized by a preliminary X-ray structure determination. However, the same reaction of 1,1′-Fc′(CH₂PH₂)₂with [Mo(CO)₄(pip)₂] gave [1,1′-Fc′(CH₂PH₂)₂Mo(CO)₄] and the dimer [1,1′-Fc′(CH₂PH₂)₂Mo(CO)₄]₂, characterized by electrospray mass spectrometry. 1,1′-Fc′[CH₂PH₂Mo(CO)₅]₂ and 1,2-Fc″[CH₂PH₂Mo(CO)₅]₂ were likewise prepared from the phosphines and excess [Mo(CO)₅(THF)]

Experimental investigation of small diameter two-phase closed thermosyphons charged with water, FC-84, FC-77 and FC-3283

Copyright © 2009 Elsevier Ltd. All rights reserved.An experimental investigation of the performance of thermosyphons charged with water as well as the dielectric heat transfer liquids FC-84, FC-77 and FC-3283 has been carried out. The copper thermosyphon was 200 mm long with an inner diameter of 6 mm, which can be considered quite small compared with the vast majority of thermosyphons reported in the open literature. The evaporator length was 40 mm and the condenser length was 60 mm which corresponds with what might be expected in compact heat exchangers. With water as the working fluid two fluid loadings were investigated, that being 0.6 ml and 1.8 ml, corresponding to approximately half filled and overfilled evaporator section in order to ensure combined pool boiling and thin film evaporation/boiling and pool boiling only conditions, respectively. For the Fluorinert™ liquids, only the higher fill volume was tested as the aim was to investigate pool boiling opposed to thin film evaporation. Generally, the water-charged thermosyphon evaporator and condenser heat transfer characteristics compared well with available predictive correlations and theories. The thermal performance of the water-charged thermosyphon also outperformed the other three working fluids in both the effective thermal resistance as well as maximum heat transport capabilities. Even so, FC-84, the lowest saturation temperature fluid tested, shows marginal improvement in the heat transfer at low operating temperatures. All of the tested Fluorinert™ liquids offer the advantage of being dielectric fluids, which may be better suited for sensitive electronics cooling applications and were all found to provide adequate thermal performance up to approximately 30–50 W after which liquid entrainment compromised their performance

Where are Bottlenecks in NK Fitness Landscapes?

Usually the offspring-parent fitness correlation is used to visualize and analyze some caracteristics of fitness landscapes such as evolvability. In this paper, we introduce a more general representation of this correlation, the Fitness Cloud (FC). We use the bottleneck metaphor to emphasise fitness levels in landscape that cause local search process to slow down. For a local search heuristic such as hill-climbing or simulated annealing, FC allows to visualize bottleneck and neutrality of landscapes. To confirm the relevance of the FC representation we show where the bottlenecks are in the well-know NK fitness landscape and also how to use neutrality information from the FC to combine some neutral operator with local search heuristic

Fragile phase stability in (1-x)Pb(Mg1/3Nb2/3O3)-xPbTiO3 crystals: A comparisons of [001] and [110] field-cooled phase diagrams

Phase diagrams of [001] and [110] field-cooled (FC) (1-x)Pb(Mg1/3Nb2/3O3)-xPbTiO3 or PMN-xPT crystals have been constructed, based on high-resolution x-ray diffraction data. Comparisons reveal several interesting findings. First, a region of abnormal thermal expansion above the dielectric maximum was found, whose stability range extended to higher temperatures by application of electric field (E). Second, the rhombohedral (R) phase of the ZFC state was replaced by a monoclinic MA in the [001] FC diagram, but with monoclinic MB in the [110] FC. Third, the monoclinic MC phase in ZFC and [001] FC diagram was replaced by an orthorhombic (O) phase in the [110] FC. Finally, in the [001] FC diagram, the phase boundary between tetragonal (T) and MA was extended to lower PT contents (x=0.25); whereas in the [110] FC diagram, this extended region was entirely replaced by the O phase. These results clearly demonstrate that the phase stability of PMN-xPT crystals is quite fragile, depending not only on modest changes in E, but also on the direction along which that E is applied.Comment: 13 pages, 8 figures, 1 tabl

pH Dependence and Stoichiometry of Binding to the Fc Region of IgG by the Herpes Simplex Virus Fc Receptor gE-gI

Herpes simplex virus type 1 encodes two glycoproteins, gE and gI, that form a heterodimer on the surface of virions and infected cells. The gE-gI heterodimer has been implicated in cell-to-cell spread of virus and is a receptor for the Fc fragment of IgG. Previous studies localized the gE-gI-binding site on human IgG to a region near the interface between the CH2 and CH3 domains of Fc, which also serves as the binding site for bacterial and mammalian Fc receptors. Although there are two potential gE-gI-binding sites per Fc homodimer, only one gE-gI heterodimer binds per IgG in gel filtration experiments. Here we report production of recombinant human Fc molecules that contain zero, one, or two potential gE-gI-binding sites and use them in analytical ultracentrifugation experiments to show that two gE-gI heterodimers can bind to each Fc. Further characterization of the gE-gI interaction with Fc reveals a sharp pH dependence of binding, with KD values of ~340 and ~930 nM for the first and second binding events, respectively, at the slightly basic pH of the cell surface (pH 7.4), but undetectable binding at pH 6.0. This strongly pH-dependent interaction suggests a physiological role for gE-gI dissociation from IgG within acidic intracellular compartments, consistent with a mechanism whereby herpes simplex virus promotes intracellular degradation of anti-viral antibodies

Evaluation of Febrile Convulsion; prevalence & clinical manifestations among children under 6 years referring to south Health Centers in Tehran on 2008

Objective: The present study was designed to evaluate the frequency & clinical manifestations of the Febrile Convulsion in children under 6 years in an Iranian sample. Patients & Methods: 600 patients between 3 months – 6 years (333female & 267 male with age mean 21.8 ± 16.2 months) referring to south Health Centers in Tehran were selected randomly. They were evaluated on demographic data(age, gender, birth priority), socioeconomic level(parents education level, parents family relationship & number of children), perinatal history(birth weight, birth age, mother's age during pregnancy), medical history(neurological disease, FC or epilepsy in family) and clinical manifestations(type & duration of FC, remitting etc) Results: The prevalence of FC was seen on 39 patients(6.5%). 8.1% of females & 4.5% of males had FC(p=0.074.( The mean age of patients 38.6± 15.8 months) had significantly difference(Mean Difference:17.9, 95%CI:13.5-22.45; p<0.001). the difference between two genders was not significant. There was no relationship between the prevalence of FC and parents family relationship and also paternal education level. Maternal education significantly influenced the FC prevalence (p<0.001). There was no relationship between the prevalence of FC and maternal age during pregnancy, number of children and birth priority (Mean Difference:405.2, 95%CI:229.9-580.4; p<0.001). There was no relationship between the prevalence of FC and birth age and type of birth. Positive family history of FC was significantly influenced the prevalence of FC (p<0.001). The relation between the prevalence of FC and positive history in mother, father & other family children was significantly different too (respectively p=0.034, p<0.001and p<0.001). Positive history of epilepsy was significantly influenced the prevalence of FC (p<0.001);The same as positive history of epilepsy in mother, father and other family children(all p<0.001). The prevalence of FC was significantly higher among children with positive history of epilepsy(p<0.001). Mean age of FC first attack WAS 23.3 ± 7.8 months. The duration of attack was reported on less than 1 minute in 17.9%, between 1-5 minutes among 64.1%, between 10_15 minutes in 10.3%, 5.1% more than 15 minutes and more than 30 minutes in 2.6%. 92.3% of children had simple FC and 7.7% had complex one. Remitting was seen on 35.9% of patients. Number of remitting was one in 30.8% and two in 5.1% of patients. Conclusion : We detect a high prevalence of FC among Iranian chilredn and a statistically significant relationship between maternal education level and job, positive family history of FC and also Epilepsy. Being aware of these factors helps in reducing the parents stress & increasing the patients' quality of life

On elements in algebras having finite number of conjugates

Let $R$ be a ring with unity and $U(R)$ its group of units. Let $\Delta U=\{a\in U(R)\mid [U(R):C_{U(R)}(a)]<\infty\}$ be the $FC$-radical of $U(R)$ and let $\nabla(R)=\{a\in R\mid [U(R):C_{U(R)}(a)]<\infty\}$ be the $FC$-subring of $R$. An infinite subgroup $H$ of $U(R)$ is said to be an $\omega$-subgroup if the left annihilator of each nonzero Lie commmutator $[x,y]$ in $R$ contains only finite number of elements of the form $1-h$, where $x,y \in R$ and $h\in H$. In the case when $R$ is an algebra over a field $F$, and $U(R)$ contains an $\omega$-subgroup, we describe its $FC$-subalgebra and the $FC$-radical. This paper is an extension of [1].Comment: 8 pages, AMS-Te