An atomic beam source for fast loading of a magneto-optical trap under high vacuum

We report on a directional atomic beam created using an alkali metal dispenser and a nozzle. By applying a high current (15 A) pulse to the dispenser at room temperature we can rapidly heat it to a temperature at which it starts dispensing, avoiding the need for preheating. The atomic beam produced is capable of loading 90% of a magneto-optical trap (MOT) in less than 7 s while maintaining a low vacuum pressure of <10(-11) Torr. The transverse velocity components of the atomic beam are measured to be within typical capture velocities of a rubidium MOT. Finally, we show that the atomic beam can be turned off within 1.8 s.     

Gas composition modeling in a reformed Methanol Fuel Cell system using adaptive Neuro-Fuzzy Inference Systems

This work presents a method for modeling the gas composition in a Reformed Methanol Fuel Cell system. The method is based on Adaptive Neuro-Fuzzy-Inference-Systems which are trained on experimental data. The developed models are of the H₂, CO₂, CO and CH₃OH mass flows of the reformed gas. The ANFIS models are able to predict the mass flows with mean absolute errors for the H₂ and CO₂ models of less than 1% and 6.37% for the CO model and 4.56% for the CH₃OH model.     

Conducting block copolymers. Towards a polymer pn- junction

Summary The synthesis of polyphenylacetylene (1), polypentafluorophenylacetylene (2) and the block copolymer of 1 and 2 polyphenylacetylene-polypentafluorophenylacetylene (3) using a Rhodium catalysed living polymerisation reaction is presented. Photoelectron spectroscopy of thin films of the individual polymers using 50eV photons from a synchrotron allowed for the determination of the position of the the electronic energy levels, ionisation potentials and the vacuum level shift which indicated that the block copolymer organises at the gold substrate surface such that the fluorinated part of the copolymer extends towards the air interface. Pulse radiolysis time resolved microwave conductivity (PR-TRMC) allowed for the determination of the minimum carrier mobilities and the carrier lifetimes. The sum of carrier mobilities, _min, were respectively 5.2·10^–7, 6.3·10^–7 and 3.2·10^–7m² V^–1 s^–1 and the first half life, _1/2, was 2.0, 1.5 and 1.0 s in 1, 2 and 3. The study shows that it is possible to make conducting block copolymers by the rhodium catalysed polymerisation of arylacetylenes with different electronic energies that organises at the surface giving rise to electronic properties that approach analogy to the traditional inorganic semiconductor pn-junctions.     

Probing the Secondary Structure of Individual Aβ40 Amorphous Aggregates and Fibrils by AFM-IR Spectroscopy

Structural characterization of aggregates and fibrils of the Aβ protein is pivotal to the molecular-level elucidation of Alzheimer's disease (AD). AFM-IR spectroscopy provides nanoscale resolution, and thus allows the interrogation of individual aggregates and fibrils. During aggregation of Aβ, we observed mainly disordered Aβ at t=15 min, but substantial structural diversity including the co-existence of parallel and antiparallel β-sheets within a large amorphous aggregate at t=2 hours, while fibrils exhibited the expected signature of parallel β-sheets at t=1 week. The resonance observed for parallel β-sheets at t=2 hours coincides with that observed for fibrils (at 1634 cm⁻¹), thus indicating that fibril-like species exist within the large aggregates. Therefore, nucleation might occur within such species, in analogy to current theories of protein crystallization in which nucleation occurs within large protein clusters. Cu²⁺ perturbs Aβ aggregation, catalysing rapid formation of amorphous aggregates with diverse secondary structure, but inhibiting fibril growth.     

The effect of forming stresses on the sintering of ultra-fine Ce0.9Gd0.1O2−δ powders

The effect of particle and pore arrangement on sintering and densification of ultra-fine (～130 nm) Ce_0.9Gd_0.1O_2?δ powder was evaluated. The common understanding that higher initial density of a ceramic network leads to a higher sintered density is not valid for fine powders, which have extremely good sinterability when there is a favourable particle packing. The effect of the applied stresses during forming (which produce different particle packing arrangements) was investigated by forging green bodies by different shaping techniques, including casting, and cold isostatic pressing. Samples formed with techniques that apply low levels of stress had a particle arrangement which significantly enhanced sintering at low temperature, compared to those prepared by high stress techniques. The sample geometry, heat treatment for organic removal and the initial density of the green body had a negligible effect on the final density when the ratio of the pore size to particle size was around 1.     

Developing a molecular platform for potential carbon dioxide fixing

This paper presents an attempt to develop a new system for fixing carbon dioxide from the atmosphere. The proposed molecular system has been designed to have the capacity to spontaneously bind CO₂ from the atmosphere with high affinity. The molecular system is furthermore designed to have the ability to liberate CO₂ at a later stage in the process, i.e., in a separate compartment. The liberated CO₂ presents a carbon neutral way of obtaining pure CO₂. The proposed molecular system is based on a small stable organic molecule that potentially have two forms: one without bound CO₂ and one with bound CO₂. One class of molecules that undergo a reaction compatible with our purposal is the merocyanine dyes that exhibit photochromic properties. Based on this structural class of molecules, a system for the potential fixing of CO₂ has been developed.     

Statistical mechanical model for the formation of octahedral silicon in phosphosilicate glasses

Unlike ambient pressure silicate glasses, some phosphosilicate glasses contain sixfold-coordinated silicon (Si⁶) units even when prepared at ambient pressure. The variation in the fraction of Si⁶ with composition remains a topic of interest, both for technological applications of phosphosilicate glasses and for fundamental understanding of the glass structure. In this work, we use statistical mechanical modeling to predict the composition–structure relationships in Na₂O–P₂O₅–SiO₂ and CaO–P₂O₅–SiO₂ glasses. This is achieved by accounting for the enthalpic and entropic contributions to the interactions between each pairwise modifier ion and structural unit. The initial enthalpy parameters are obtained based on experimental structural data for binary Na₂O–SiO₂, CaO–SiO₂, Na₂O–P₂O₅, and CaO–P₂O₅ glasses, which can then be transferred to predict the structure of mixed former glasses. This approach has previously been used to predict the short-range structure of borosilicate and aluminoborate glass systems. However, here we show that the formation of Si⁶ must be specifically included to make accurate predictions of the composition–structure relationships in phosphosilicate glasses. After incorporating the formation mechanism of Si⁶ in the statistical mechanics model, we find an excellent agreement between model predictions and experimental structure data for Na₂O–P₂O₅–SiO₂ and CaO–P₂O₅–SiO₂ glasses.     

PowerForms: Declarative client-side form field validation

All uses of HTML forms may benefit from validation of the specified input field values. Simple validation matches individual values against specified formats, while more advanced validation may involve interdependencies of form fields. There is currently no standard for specifying or implementing such validation. Today, CGI programmers often use Perl libraries for simple server-side validation or program customized JavaScript solutions for client-side validation. We present PowerForms, which is an add-on to HTML forms that allows a purely declarative specification of input formats and sophisticated interdependencies of form fields. While our work may be seen as inspiration for a future extension of HTML, it is also available for CGI programmers today through a preprocessor that translates a PowerForms document into a combination of standard HTML and JavaScript that works on all combinations of platforms and browsers. The definitions of PowerForms formats are syntactically disjoint from the form itself, which allows a modular development where the form is perhaps automatically generated by other tools and the formats and interdependencies are added separately. PowerForms has a clean semantics defined through a fixed-point process that resolves the interdependencies between all field values. Text fields are equipped with status icons (by default traffic lights) that continuously reflect the validity of the text that has been entered so far, thus providing immediate feed-back for the user. For other GUI components the available options are dynamically filtered to present only the allowed values. PowerForms are integrated into the system for generating interactive Web services, but is also freely available in an Open Source distribution as a stand-alone package.     

冰山住宅

冰山住宅的外形轮廓清晰、线条分明,11个白色的峰顶为奥尔胡斯天际线增添了浓墨重彩的一笔,无论从向陆面还是从临海面看去都是如此.项目地理位置优越,位于奥尔胡斯新区的黄金地段——奥尔胡斯东岸最远端的港湾区,共包含208间公寓.正如许多其他日益破败的工业港口区一样,先前的奥尔胡斯集装箱港正逐渐被改造成为一个充满活力的新社区,各种各样的居住、教育机构、办公、零售、运动和休闲功能单元一应俱全。     

Applying rotary jet heads for mixing and mass transfer in a forced recirculation tank reactor system

An approximation to an ideally mixed tank reactor can be obtained by vigorous stirring with mechanical mixers. For an aerated reactor the gas dispersion contributes to the mixing process. Mixing can also be achieved by recirculation of a portion of the liquid through either an internal or an external loop.In this study, we determine mixing times in water and CMC solutions and oxygen mass transfer coefficients in water for a tank reactor system where a small fraction of the total liquid volume is rapidly circulated through an external loop and injected through the nozzles of rotary jet heads at 1-9 bar gauge pressure into the bulk liquid. Liquid feed can be added to the bulk volume or it may be injected into the pressurized recirculation loop. Gas is always fed to the recirculation loop, and the heat of reaction is removed in a plate-type heat exchanger inserted in the recirculation loop. The system has a very simple design with no internal baffles or heat exchange area, and between batches the rotary jet heads are used for cleaning in place.Mixing time decreases and mass transfer increases with increasing circulation flow rate. For nozzle diameters between 5.5 and and with one or two rotary jet heads, it is shown that a remarkable saving in power input for a fixed mixing time or mass transfer coefficient can be obtained by using a large nozzle diameter and two rather than one rotary jet heads.At the experimental conditions of the study the system is scaleable by simple formulas, and the power input to achieve a certain mixing time is proportional to the bulk liquid volume.