玉米C型细胞质雄性不育特异片段的分离及验证

对一套玉米同核异质不育系及保持系(包括N48-2、T48-2、C48-2、S48-2)的线粒体DNA进行了扩增片断长度多态性(AFLP)分析比较.从选择性扩增产物中筛选到了一条C48-2所特有的差异条带C48-223.对C48-223进行克隆、测序分析表明,它是玉米C型细胞质雄性不育线粒体atp6基因编码序列的一部分.Southern、Northern杂交分析证实了C48-223在C48-2线粒体上的特异性.这说明该差异片段有可能同C型细胞质雄性不育性状的表现有关.     

Real-time all-optical quality of service monitoring by use of correlation and a network protocol to exploit it

We propose to use optical correlation to measure the quality of an optical link in real time, staying completely within the optical domain. We transmit a test signal of 010 and correlate the received (degraded) signal with 010. The strength and shape of the output measure dispersion and attenuation in just 3 bit periods (75 ps at 40 Gb/s) compared with minutes by traditional methods. Correlation becomes feasible owing to the recent development of tapped delay lines with very large numbers of taps. We present simulations showing that this technique can detect attenuation, dispersion, noise, and jitter. With this instantaneous quality-of-service information available to all nodes in a network, new protocols will enable the network to select paths based on quality, allowing service providers to take into account the system's physical impairments when selecting new light paths or when restoring existing ones and to guarantee varying levels of service. We present one such protocol.     

A facile and general approach to polynary semiconductor nanocrystals via a modified two-phase method

Cu(2)ZnSnS(4) nanocrystals were synthesized through a modified two-phase method and characterized with transmission electron microscopy (TEM), powder x-ray diffraction (XRD) and UV-vis spectroscopy. Inorganic metal salts were dissolved in the polar solvent triethylene glycol (TEG) and then transferred into the non-polar solvent 1-octadecene (ODE) by forming metal complexes between metal ions and octadecylamine (ODA). Since nucleation and growth occur in the single phase of the ODE solution, nanocrystals could be produced with qualities similar to those obtained through the hot-injection route. Balancing the reactivity of the metal precursors is a key factor in producing nanocrystals of a single crystalline phase. We found that increasing the reaction temperature increases the reactivity of each of the metal precursors by differing amounts, thus providing the necessary flexibility for obtaining a balanced reactivity that produces the desired product. The versatility of this synthesis strategy was demonstrated by extending it to the production of other polynary nanocrystals such as binary (CuS), ternary (CuInS(2)) and pentanary (Cu(2 - x)Ag(x)ZnSnS(4)) nanocrystals. This method is considered as a green synthesis route due to the use of inorganic metal salts as precursors, smaller amounts of coordinating solvent, shorter reaction time and simpler post-reaction treatment.     

Electron transport properties of deformed potassium and a potassium-rubidium alloy from 0.08 to 4.2 K

Measurements have been performed of electrical resistivity and thermoelectric ratioG on deformed samples of potassium as well as of on a deformed 0.077 at %KRb alloy. A large anomaly in (T) forT<0.5 K is ascribed to electrons interacting with vibrating dislocations and it is shown that the data are consistent with a model of Gantmakher and Kulesko in which the scattering arises from local phonon modes associated with the dislocations. ForT>1 K, an increase in (T) is ascribed to the suppression of phonon drag by the dislocations. The latter is qualitatively confirmed by theG measurements. A maximum inG at 0.5 K is observed when dislocations are present. The two effects in (T) outlined above are so large that the change in the electron-electron scattering contribution to due to deformation cannot be precisely determined.     

Detailed design and transport properties of a helium droplet nozzle from 5 to 50 K

This paper reports our efforts to engineer a robust, user-friendly, and broadly tunable helium droplet nozzle, and to quantitatively measure its thermal and mass transport performance. In addition to describing the physical design in detail, we report helium throughput measurements for a 6.4 μm diameter nozzle over stagnation conditions ranging from 5 to 50 K and 10 to 100 bar. The measured flow rates were in excellent agreement with those predicted by a simple effusive flow model for nozzle temperatures above 20 K, but were systematically lower for both sub-critical and super-critical jets as the temperature was lowered. The helium flow through a 500 μm skimmer was also measured, and the skimmed fraction was found to vary by two orders of magnitude over the range of stagnation conditions investigated. These results indicate a substantial narrowing of the total jet angle spread from ～90° to 5° at temperatures below 10 K. Efforts to image the low temperature jet with Schlieren and shadowgraph techniques were unsuccessful. These details combined with previously reported theory and experiments on the droplet size distributions provide the necessary foundation to predict cluster production rates and to customize nozzle/pump designs for specific applications.     

Application of mid-infrared spectroscopy to the development and transfer of a manufacturing process for an active pharmaceutical ingredient

The use of in situ mid-infrared spectroscopy to support the development of a pharmaceutical manufacturing process is disclosed. Data on this two-stage telescoped reaction from several reaction scales (<50 mL to 1600 liters) and at multiple manufacturing locations is shown. In addition to providing data on both reactions in the telescope, the mid-IR data has been used to monitor an intermediate distillation operation and therefore it has been possible to profile the whole process. Data is also shown on aliquot addition during the first chemical transformation, which is used to check the instrumentation.     

Measurement of the enthalpy and specific heat of a Be2C-graphite-UC2 reactor fuel material to 1980 K

The enthalpy and specific heat of a Be₂C-Graphite-UC₂ composite nuclear fuel material have been measured over the temperature range 298–1980 K using both differential scanning calorimetry and liquid argon vaporization calorimetry. The fuel material measured was developed at Sandia National Laboratories for use in pulsed test reactors. The material is a hot-pressed composite consisting of 40 vol% Be₂C, 49.5 vol% graphite, 3.5 vol% UC₂, and 7.0 vol% void. The specific heat was measured with the differential scanning calorimeter over the temperature range 298–950 K, while the enthalpy was measured over the range 1185–1980 K with the liquid argon vaporization calorimeter. The normal spectral emittance at a wavelength of 6.5×10^–5 cm was also measured over the experimental temperature range. The combined experimental enthalpy data were fit using a spline routine and differentiated to give the specific heat. Comparison of the measured specific heat of the composite to the specific heat calculated by summing the contributions of the individual components indicates that the specific heat of the Be₂C component differs significantly from literature values and is approximately 0.56 cal · g^–1 · K ^–1 (2.3×10³J · kg^–1 · K ^–1) for temperatures above 1000 K.     

Uniform-load and actuator influence functions of a thin or thick annular mirror: application to active mirror support optimization

Explicit analytical expressions are derived for the elastic deformation of a thin or thick mirror of uniform thickness and with a central hole. Thin-plate theory is used to derive the general influence function, caused by uniform and/or discrete loads, for a mirror supported by discrete points. No symmetry considerations of the locations of the points constrain the model. An estimate of the effect of the shear forces is added to the previous pure bending model to take into account the effect of the mirror thickness. Two particular cases of general influence are considered: the actuator influence function and the uniform-load (equivalent to gravity in the case of a thin mirror) influence function for a ring support of k discrete points with k-fold symmetry. The influence of the size of the support pads is studied. A method for optimizing an active mirror cell is presented that couples the minimization of the gravity influence function with the optimization of the combined actuator influence functions to fit low-order aberrations. These low-spatial-frequency aberrations can be of elastic or optical origin. In the latter case they are due, for example, to great residual polishing errors corresponding to the soft polishing specifications relaxed for cost reductions. Results show that the correction range of the active cell can thus be noticeably enlarged, compared with an active cell designed as a passive cell, i.e., by minimizing only the deflection under gravitational loading. In the example treated here of the European Southern Observatory's New Technology Telescope I show that the active correction range can be enlarged by ~50% in the case of third-order astigmatic correction.     

The long-term decrease of 90Sr availability in the environment and its transfer to man after a nuclear fallout

Due to its long physical half-life, and the fact that its long-term mobility in the environment as well as its radiotoxicity is higher than that of 137Cs, the long-term bio-availability of 90Sr in the environment is of importance with regard to the long-term population exposure after fallout from nuclear weapons detonations or a severe reactor accident. It will also substantially influence the time-span required until re-utilisation of highly contaminated territory is possible again. An assessment of the long-term decrease of the activity concentration in all foodstuffs relevant for internal exposure after severe 90Sr fallout was performed. The observed effective half-lives were approximately 1.8-2.1 years in the first 2-3 years after the end of fallout and 8-10 years in the following three decades. This is equivalent to a biological half-life of about 13.2 years and results in a total 50 year dose of 6.2 times the first year exposure. Due to this decline in 90Sr-availability, the average annual activity intake of 90Sr in Austria has decreased from 840 Bq at the climax of the nuclear weapons tests to about 42 Bq in 1997 for adults, and from 500 Bq to about 35 Bq for 1 year old infants. This is equivalent to a 90Sr ingestion dose of 1.2 microSv for adults and 2.5 microSv for 1 year old infants in 1997 or less than 0.4% of the ingestion dose by natural radionuclides in the diet.     

A decision theoretic approach to an accident sequence: when feedwater and auxiliary feedwater fail in a nuclear power plant

This study applies a decision theoretic perspective on a severe accident management sequence in a processing industry. The sequence contains loss of feedwater and auxiliary feedwater in a boiling water nuclear reactor (BWR), which necessitates manual depressurization of the reactor pressure vessel to enable low pressure cooling of the core. The sequence is fast and is a major contributor to core damage in probabilistic risk analyses (PRAs) of this kind of plant. The management of the sequence also includes important, difficult and fast human decision making. The decision theoretic perspective, which is applied to a Swedish ABB-type reactor, stresses the roles played by uncertainties about plant state, consequences of different actions and goals during the management of a severe accident sequence. Based on a theoretical analysis and empirical simulator data the human error probabilities in the PRA for the plant are considered to be too small. Recommendations for how to improve safety are given and they include full automation of the sequence, improved operator training, and/or actions to assist the operators' decision making through reduction of uncertainties, for example, concerning water/steam level for sufficient cooling, time remaining before insufficient cooling level in the tank is reached and organizational cost-benefit evaluations of the events following a false alarm depressurization as well as the events following a successful depressurization at different points in time. Finally, it is pointed out that the approach exemplified in this study is applicable to any accident scenario which includes difficult human decision making with conflicting goals, uncertain information and with very serious consequences.     

Preparation and characterization of polymeric plasticized membranes (PPM) embedding a crown ether carrier application to copper ions transport

Polymeric plasticized membranes (PPM) are a new perspective to solve the stability problems of supported liquid membranes to perform the simultaneous separation, concentration and purification of valuable species from aqueous solutions.Cellulose triacetate (CTA) membranes containing the crown ether dibenzo-18-crown-6 (DB18C6) as a fixed carrier were prepared and their performance tested for the transport of copper(II) ions. This study showed that PPM properties were influenced by the membrane composition. The transport studies revealed that diffusion rate was dependent on film thickness, the presence of a plasticizer, 2-nitrophenyloctylether, which plays also a critical role on the membrane physical characteristics (especially malleability) and the quantity of fixed crown ether. Porosimetry analyses showed conversely to other works with different carriers that all the membranes prepared are not porous for all membrane compositions. However, SEM analysis revealed a porous texture when the quantity of crown ether is higher than that of CTA. FTIR, X-ray and TGA characterizations showed that all the constituents of the membrane remain unaltered within the membrane without chemical interactions between them (no presence of new bonds in the FTIR spectra). Hence, transport mechanism of the copper(II) ions seems to be a jumping from site to site.     

QCM-D analysis of binding mechanism of phage particles displaying a constrained heptapeptide with specific affinity to SiO2 and TiO2

A growing number of peptides capable of specifically recognizing inorganic materials have been reported, incrementally increasing the potential to harness peptides as a biological linker to bridge biomolecules and inorganic materials at nanometer scale. In this study, we identified disulfide bond constrained heptapeptides with specific binding affinity to SiO2 and TiO2 using a phage display technique. Interestingly, two of the phage surface displayed peptides enriched with basic amino acid residues, STB1 (HKKPSKS) and STB2 (TKRNNKR), showed a cross binding affinity to both metal oxides. To understand the underlying binding mechanism, binding behaviors of phage particles harboring the STB1 (a high-frequency heptapeptide exhibiting dual binding affinity to both metal oxides) were investigated in a wide pH range using quartz crystal microbalance with energy dissipation measurement (QCM-D). It was found that the binding of STB1-harboring phages to the two metal oxides was clearly mediated by the peptide moiety displayed on the phage surface in a pH-dependent manner, indicating that the binding is largely governed by electrostatic interaction. Furthermore, the interpretation of QCM-D signals (i.e., frequency shift and dissipation shift), with the aid of AFM image analysis of the phage particles bound on the surface of the two metal oxides, elucidated whether the nature of phage (or the displayed peptide) binding to the metal oxides is largely specific or nonspecific.     

Application of the theory of random processes to combined desiccation and pneumatic transport of solid particles with a turbulent gas stream

The method of mathematical statistics is used for analyzing the desiccation of solid particles during pneumatic transport, with the effect of turbulent gas fluctuations on the motion of particles taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 2, pp. 299–308, August, 1973.     

On the applicability of a semi-analytical approach to determining the transient electron transport response of gallium arsenide, gallium nitride, and zinc oxide

We critically examine the applicability of the semi-analytical approach of Shur (M. Shur, Electron Lett 12, 615 (1976)) in evaluating the transient electron transport response of gallium arsenide, gallium nitride, and zinc oxide. In particular, we contrast results obtained using this semi-analytical approach of Shur with those obtained using Monte Carlo simulations of the electron transport. Our approach will be to examine the response of an ensemble of electrons to the application of a constant and uniform applied electric field. For the purposes of this analysis, three aspects of the transient electron transport response will be considered: (1) the dependence of the electron drift velocity on the time elapsed since the onset of the applied electric field, (2) the dependence of the average electron energy on the time elapsed since the onset of the applied electric field, and (3) the dependence of the average electron displacement on the time elapsed since the onset of the applied electric field. The results obtained show that this semi-analytical approach of Shur produces results that are very similar to those produced using Monte Carlo simulations. Thus, this semi-analytical approach of Shur should be applicable for the treatment of non-uniform and time-varying electric fields, making it a useful tool for the treatment of the transient electron transport response within electron device configurations.     

A historical overview of probabilistic risk assessment development and its use in the nuclear power industry: a tribute to the late Professor Norman Carl Rasmussen

This paper reviews the historical development of the probabilistic risk assessment (PRA) methods and applications in the nuclear industry. A review of nuclear safety and regulatory developments in the early days of nuclear power in the United States has been presented. It is argued that due to technical difficulties for measuring and characterizing uncertainties and concerns over legal challenges, safety design and regulation of nuclear power plants has primarily relied upon conservative safety assessment methods derived based on a set of design and safety principles. Further, it is noted that the conservatism adopted in safety and design assessments has allowed the use of deterministic performance assessment methods. This approach worked successfully in the early years of nuclear power epoch as the reactor design proved to be safe enough. However, it has been observed that as the conservative approach to design and safety criteria proved arbitrary, and yielded inconsistencies in the degree to which different safety measures in nuclear power plants protect safety and public heath, the urge for a more consistent assessment of safety became apparent in the late 1960s. In the early 1970s, as a result of public and political pressures, then the US Atomic Energy Commission initiated a new look at the safety of the nuclear power plants through a comprehensive study called ‘Reactor Safety Study’ (WASH-1400, or ‘Rasmussen Study’—after its charismatic study leader Professor Norman Rasmussen of MIT) to demonstrate safety of the nuclear power plants. Completed in October 1975, this landmark study introduced a novel probabilistic, systematic and holistic approach to the assessment of safety, which ultimately resulted in a sweeping paradigm shift in safety design and regulation of nuclear power in the United States in the turn of the Century. Technical issues of historic significance and concerns raised by the subsequent reviews of the Rasmussen Study have been discussed. Effect of major events and developments such as the Three Mile Island accident and the Nuclear Regulatory Commission and the Nuclear Industry sponsored studies on the tools, techniques and applications of the PRA that culminated in the present day risk-informed initiatives has been discussed.