Stereoisomerism in pentaerythritol-bridged cyclotriphosphazene tri-spiranes: spiro and ansa 1,3-propanediyldioxy disubstituted derivatives

Four isomeric products were isolated and purified from the reaction of 1,3-propanediol with the tetra-spirane cyclophosphazene-organophosphate compound (1): viz. the di-monospiro (2a), di-monoansa (2b) and two monospiro-monoansa derivatives (2c) and (2d). It is shown by 31P NMR spectroscopy on addition of a chiral solvating agent (CSA) that both the di-monospiro (2a) and di-monoansa (2b) derivatives are racemates, as expected, whereas no splitting of NMR signals occurred on addition of CSA to solutions of (2c) and (2d). It is found by X-ray crystallography that the two monospiro-monoansa spirane derivatives, (2c) and (2d), are meso diastereoisomers, which represent a new case of the stereochemistry of bis di-substituted cyclophosphazene derivatives of (1). It is also observed from the 31P NMR spectrum of the reaction mixture, supported by the yields of pure compounds, that formation of a spiro group is about 4.5 times more likely than that of an ansa moiety under the conditions of the reaction

The radiating part of circular sources

An analysis is developed linking the form of the sound field from a circular source to the radial structure of the source, without recourse to far-field or other approximations. It is found that the information radiated into the field is limited, with the limit fixed by the wavenumber of source multiplied by the source radius (Helmholtz number). The acoustic field is found in terms of the elementary fields generated by a set of line sources whose form is given by Chebyshev polynomials of the second kind, and whose amplitude is found to be given by weighted integrals of the radial source term. The analysis is developed for tonal sources, such as rotors, and, for Helmholtz number less than two, for random disk sources. In this case, the analysis yields the cross-spectrum between two points in the acoustic field. The analysis is applied to the problems of tonal radiation, random source radiation as a model problem for jet noise, and to noise cancellation, as in active control of noise from rotors. It is found that the approach gives an accurate model for the radiation problem and explicitly identifies those parts of a source which radiate.Comment: Submitted to Journal of the Acoustical Society of Americ

Accurate prediction of gene feedback circuit behavior from component properties

A basic assumption underlying synthetic biology is that analysis of genetic circuit elements, such as regulatory proteins and promoters, can be used to understand and predict the behavior of circuits containing those elements. To test this assumption, we used time‐lapse fluorescence microscopy to quantitatively analyze two autoregulatory negative feedback circuits. By measuring the gene regulation functions of the corresponding repressor–promoter interactions, we accurately predicted the expression level of the autoregulatory feedback loops, in molecular units. This demonstration that quantitative characterization of regulatory elements can predict the behavior of genetic circuits supports a fundamental requirement of synthetic biology

Assessing Human Iron Kinetics Using Stable Iron Isotopic Techniques

Stable iron isotope techniques are critical for developing strategies to combat iron deficiency anemia, a leading cause of global disability. There are four primary stable iron isotope methods to assess ferrokinetics in humans. (i) The fecal recovery method applies the principles of a metabolic balance study but offers enhanced accuracy because the amount of iron isotope present in feces can be directly traced back to the labeled dose, distinguishing it from endogenous iron lost in stool from shed intestinal cells. (ii) In the plasma isotope appearance method, plasma samples are collected for several hours after oral dosing to evaluate the rate, quantity, and pattern of iron absorption. Key metrics include the time of peak isotope concentration and the area under the curve. (iii) The erythrocyte iron incorporation method measures iron bioavailability (absorption and erythrocyte iron utilization) from a whole blood sample collected 2 weeks after oral dosing. Simultaneous administration of oral and intravenous tracers allows for separate measurements of iron absorption and iron utilization. These three methods determine iron absorption by measuring tracer concentrations in feces, serum, or erythrocytes after administration of a tracer. In contrast, (iv) in iron isotope dilution, an innovative new approach, iron of natural composition acts as the tracer, diluting an ad hoc modified isotopic signature obtained via prior isotope administration and equilibration with body iron. This technique enables highly accurate long-term studies of iron absorption, loss, and gain. This review discusses the application of these kinetic methods and their potential to address important questions in hematology and iron biology

Quantum privacy and quantum coherence

We derive a simple relation between a quantum channel's capacity to convey coherent (quantum) information and its usefulness for quantum cryptography.Comment: 6 pages RevTex; two short comments added 7 October 199

Q(2) dependence of nuclear transparency for exclusive rho(0) production

Exclusive coherent and incoherent electroproduction of the rho(0) meson from H-1 and N-14 targets has been studied at the HERMES experiment as a function of coherence length (l(c)), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon (-Q(2)). The ratio of N-14 to H-1 cross sections per nucleon, called nuclear transparency, was found to increase (decrease) with increasing l(c) for coherent (incoherent) rho(0) electroproduction. For fixed l(c), a rise of nuclear transparency with Q(2) is observed for both coherent and incoherent rho(0) production, which is in agreement with theoretical calculations of color transparency

Banning Commercial Foresting: What are the Costs?

The Philippines' forest cover has suffered from massive denudation through the years due to uncontrolled and indiscriminate commercial logging. Because of this, calls for a total logging ban had been raised in various fora, including in the legislature where bills that consider the possibility of a ban are being studied. However, the possible economic costs of such ban as espoused in some studies has delayed the passage of these bills. This Policy Notes provides some economic costing based on computations that may help in firming up decisions regarding the proposed ban.forestry sector, environmental issues, environmental management

Correlations, fluctuations and stability of a finite-size network of coupled oscillators

The incoherent state of the Kuramoto model of coupled oscillators exhibits marginal modes in mean field theory. We demonstrate that corrections due to finite size effects render these modes stable in the subcritical case, i.e. when the population is not synchronous. This demonstration is facilitated by the construction of a non-equilibrium statistical field theoretic formulation of a generic model of coupled oscillators. This theory is consistent with previous results. In the all-to-all case, the fluctuations in this theory are due completely to finite size corrections, which can be calculated in an expansion in 1/N, where N is the number of oscillators. The N -> infinity limit of this theory is what is traditionally called mean field theory for the Kuramoto model.Comment: 25 pages (2 column), 12 figures, modifications for resubmissio

Thresholds for the Oxford Hip Score after total hip replacement surgery:a novel approach to postoperative evaluation

Abstract Background This is a prospective cohort study to define the thresholds to distinguish patients with a satisfactory or unsatisfactory outcome after total hip replacement (THR) based on patient-reported outcome measures (PROMs) including the Oxford Hip Score (OHS), and using patient satisfaction and patient-perceived function as global transition items. The thresholds are intended to be used as a tool in the process of determining which patients are in need of postoperative outpatient evaluation. Methods One hundred and three THR patients who had completed a preoperative questionnaire containing the OHS questionnaire were invited to complete the same questionnaire and supplementary questions at a mean of 6 (4–9) months after surgery. Correlations between outcome measures and anchors were calculated using Pearson’s correlation coefficient. Thresholds were established by receiver operating characteristic (ROC) analysis, using multiple anchors. Results Significant correlations were found between outcome measures and anchors. Thresholds were determined for outcome measures coupled with satisfaction, patient-perceived function and a combination thereof using a cut-off of 50 and 70. Conclusions We have established a set of thresholds for Oxford scores that may help determine which THR patients are in need of postoperative evaluation. These thresholds can be implemented in clinical practice. Level of evidence Level 3