平衡别墅

精选理由平衡别墅是一个让人放松又兴奋的度假屋。它体长30米,在斜坡处有个15米的悬臂用以支撑欲跌的房屋,如此特别的设计是为了最亲近地体验大自然的魅力。     

On-chip contactless four-electrode conductivity detection for capillary electrophoresis devices

In this contribution, a capillary electrophoresis microdevice with an integrated on-chip contactless four-electrode conductivity detector is presented. A 6-cm-long, 70-microm-wide, and 20-microm-deep channel was etched in a glass substrate that was bonded to a second glass substrate in order to form a sealed channel. Four contactless electrodes (metal electrodes covered by 30-nm silicon carbide) were deposited and patterned on the second glass substrate for on-chip conductivity detection. Contactless conductivity detection was performed in either a two- or a four-electrode configuration. Experimental results confirmed the improved characteristics of the four-electrode configuration over the classical two-electrode detection setup. The four-electrode configuration allows for sensitive detection for varying carrier-electrolyte background conductivity without the need for adjustment of the measurement frequency. Reproducible electrophoretic separations of three inorganic cations (K+, Na+, Li+) and six organic acids are presented. Detection as low as 5 microM for potassium was demonstrated.     

A coverslip method for controlled parallel sample introduction into arrays of (sub)nanoliter wells for quantitative analysis

We have developed a straightforward coverslip method that combines rapid sample introduction into arrays of 19.8-55.0-microm-deep microwells (prefilled with reactants) on a chip with complete sealing of these wells to avoid evaporation during optical detection. We used coverslips of 300-1500-microm-thick poly(methyl methacrylate) (PMMA) containing arrays of holes with diameters of 200 and 300 microm, and 800-microm-thick quartz slides containing arrays of holes with diameters of 100 and 200 microm. A coverslip was placed on top of a chip, thereby positioning the holes between the wells. A defined amount of aqueous sample solution was pulled between the cover and silicon nitride coated chip by means of capillary forces, resulting in entrapment of air in all wells. By partly or completely positioning the holes over the wells, air could escape through the holes, resulting in complete filling of the wells with the surrounding liquid within 0.1-0.2 s. Immediately after filling, the slide was rapidly shifted back to its original position and was pressed onto the chip for 5-30 s with a force of 1-2 kg cm(-2), resulting in complete sealing of the wells for minutes up to one-half hour. Because the well volumes of an array are identical and the wells are completely filled, reproducible assay volumes and flat menisci are obtained, making this method very suitable for quantitative analysis.     

Microfluidic applications of functionalized magnetic particles for environmental analysis: focus on waterborne pathogen detection

The continuous surveillance of drinking water is extremely important to provide early warning of contamination and to ensure continuous supplies of healthy drinking water. Isolation and detection of a particular type of pathogen present at low concentration in a large volume of water, concentrating the analyte in a small detection volume, and removing detection inhibiting factors from the concentrated sample, present the three most important challenges for water quality monitoring laboratories. Combining advanced biological detection methods (e.g., nucleic acid-based or immunology-based protocols) with microfluidics and immunomagnetic separation techniques that exploit functionalized magnetic particles has tremendous potential for realization of an integrated system for pathogen detection, in particular, of waterborne pathogens. Taking advantage of the unique properties of magnetic particles, faster, more sensitive, and more economical diagnostic assays can be developed that can assist in the battle against microbial pathogenesis. In this review, we highlight current technologies and methods used for realization of magnetic particle-based microfluidic integrated waterborne pathogen isolation and detection systems, which have the potential to comply in future with regulatory water quality monitoring requirements.     

Stability of Stones under Uniform Flow

The present technical note aims to discuss a depth-averaged turbulence parameter in relation to the incipient motion of particles. The proposed stability equation emphasizing a depth-averaged turbulence parameter, is validated for the cases of bed protection in a steep channel and on a broad-crested weir. A design diagram representing load and resistance of movement has been introduced for turbulent flow conditions in which the transport of particles or the damage to the bed protection is expressed by the critical Shields parameter.     

Integrated topology and controller optimization of motion systems in the frequency domain

In the precision mechatronics industry the limits of current technology are expanded by a very tight integration of the design disciplines involved, such as structural mechanics and control systems technology. In this article a framework is presented which allows the simultaneous and integrated design of a structure and controller. The structure is designed using topology optimization and the objectives and constraints are related to the closed-loop control performance and defined in the frequency domain. For simple examples it is shown that this approach leads to at least as good performance as a sequential approach consisting of eigenfrequency optimization followed by controller tuning, and leads to lighter designs. The framework allows rapid development of prototype designs, which may save a number of the costly design iterations which are currently made in industrial practice. Examples are found in the semiconductor industry, microscopy, micro–electromechanical devices, medical devices and robotics.     

Glass reflow on 3-dimensional micro-apertures for electrophysiological measurements on-chip

We propose a new method to fabricate micro-apertures for on-chip electrophysiological measurements of living cells. Thermal reflow of phosphosilicate glass (PSG) is applied to funnel- or nozzle-type microstructures to generate very smooth surfaces on the finalized chip. Such 3-dimensional microstructures show close similarities to fire-polished glass pipette tips. Immobilized cells fit perfectly to these structures offering a large contact area for sealing between the cell membrane and the oxide surface. A tight cell/chip-aperture seal is an important requirement for the present application. We demonstrate the formation of stable gigaseals with Chinese hamster ovary (CHO) cells for both types of microstructures without the need of any post-fabrication surface treatment. By adjusting the PSG reflow parameters, the shape of the apertures can be modified and diameters down to the sub-micrometer range may be achieved. The application of PSG reflow to MEMS fabrication is an interesting new option to create unconventional microstructures.     

Decoding stimulus-related information from single-trial EEG responses based on voltage topographies

Neuroimaging studies typically compare experimental conditions using average brain responses, thereby overlooking the stimulus-related information conveyed by distributed spatio-temporal patterns of single-trial responses. Here, we take advantage of this rich information at a single-trial level to decode stimulus-related signals in two event-related potential (ERP) studies. Our method models the statistical distribution of the voltage topographies with a Gaussian Mixture Model (GMM), which reduces the dataset to a number of representative voltage topographies. The degree of presence of these topographies across trials at specific latencies is then used to classify experimental conditions. We tested the algorithm using a cross-validation procedure in two independent EEG datasets. In the first ERP study, we classified left- versus right-hemifield checkerboard stimuli for upper and lower visual hemifields. In a second ERP study, when functional differences cannot be assumed, we classified initial versus repeated presentations of visual objects. With minimal a priori information, the GMM model provides neurophysiologically interpretable features – vis à vis voltage topographies – as well as dynamic information about brain function. This method can in principle be applied to any ERP dataset testing the functional relevance of specific time periods for stimulus processing, the predictability of subject's behavior and cognitive states, and the discrimination between healthy and clinical populations.     

New hybrid technology for planar fluxgate sensor fabrication

We have adapted a new printed circuit board (PCB) technology to the fabrication of ultraflat and sensitive fluxgate magnetic field sensors. The two outer layers of the PCB stack compose the electrical windings of fluxgates, while the inner layer is made of a micro-patterned amorphous magnetic ribbon with extremely high relative magnetic permeability (μ_r≈100 000). Two basic configurations were considered: one based on a toroidal magnetic core and the other on a rectangular core with and without an air gap. The field response and sensitivity of the fluxgate devices have been studied as a function of the gap length, the excitation current, and excitation frequency. Compared to fluxgate sensors of similar size, a relatively high sensitivity of 60 V/T was found at 30 kHz for a five-winding detection coil wound around a rectangular E-shaped magnetic core. This high performance is primarily attributable to the high-permeability magnetic core. The results clearly show the potential of this fluxgate device for application as a magnetic sensor     

Effect of activated carbon amendment on bacterial community structure and functions in a PAH impacted urban soil

We collected urban soil samples impacted by polycyclic aromatic hydrocarbons (PAHs) from a sorbent-based remediation field trial to address concerns about unwanted side-effects of 2% powdered (PAC) or granular (GAC) activated carbon amendment on soil microbiology and pollutant biodegradation. After three years, total microbial cell counts and respiration rates were highest in the GAC amended soil. The predominant bacterial community structure derived from denaturing gradient gel electrophoresis (DGGE) shifted more strongly with time than in response to AC amendment. DGGE band sequencing revealed the presence of taxa with closest affiliations either to known PAH degraders, e.g. Rhodococcus jostii RHA-1, or taxa known to harbor PAH degraders, e.g. Rhodococcus erythropolis, in all soils. Quantification by real-time polymerase chain reaction yielded similar dioxygenases gene copy numbers in unamended, PAC-, or GAC-amended soil. PAH availability assessments in batch tests showed the greatest difference of 75% with and without biocide addition for unamended soil, while the lowest PAH availability overall was measured in PAC-amended, live soil. We conclude that AC had no detrimental effects on soil microbiology, AC-amended soils retained the potential to biodegrade PAHs, but the removal of available pollutants by biodegradation was most notable in unamended soil.