Atom localization in a four-level alkaline earth atomic system

We propose an atom localization scheme for a four-level alkaline earth atom via a classical standing-wave field, and give the analytical expressions of the localization peak positions as well as the widths versus the parameters of the optical fields. We show that the probability of finding the atom at a particular position can be increased from 1/4 to 1/3 or 1/2 by adjusting the detuning of the probe field and the Rabi frequencies of the optical fields. Furthermore, the localization precision can be dramatically enhanced by increasing the intensity of the standing-wave field or decreasing the detuning of the probe field. The analytical results are quite accordant to the numerical solutions.     

Silicon Carbide-Based Extreme Environment Hybrid Design Temperature Sensor Using Optical Pyrometry and Laser Interferometry

To the best of the authors' knowledge, proposed and demonstrated is the first extreme environment temperature sensor using Blackbody (BB) radiation of a high-temperature material optical chip for coarse temperature measurement and classical Fabry-Perot (FP) laser interferometry via the same chip for fine temperature measurement. Such a hybrid design sensor can be used to accurately measure temperatures in excess of 750°C such as needed for gas turbines in power plants and aircraft engines. The proposed sensor is designed and demonstrated using an all-Silicon Carbide (SiC) probe for temperatures from 795°C to 1077°C with an estimated average measurement resolution of 0.1°C.     

Acoustic sensors for the control of liquid–solid interface evolution and chemical reactivity

Less classical than far-field acoustic investigations of solid materials and/or solid–liquid interfaces, near-field acoustic properties of an acoustic solid wave guide (tip), thin enough at its termination to present an external diameter smaller than the excitation acoustic wave wavelength, is shown to be able to probe interface properties. As a result of that, these near-field acoustic probes can play the role of chemical sensors, if chemical modifications or chemical reactions are concerned at their surface. In that context, a chemical sensor was realized by electrochemical deposition of an electron-conducting polymer (polypyrrole–biotin) on a metal tip, followed by enzyme attachment by molecular recognition process involving the biotin–avidin-specific interaction. Results from near-field acoustic showed that the enzyme modification of the polymer layer can be detected by this new acoustic sensor.     

Electrons at the surface of quantum systems

Electrons can be trapped at the surfaces and interfaces of the condensed phases of quantum matter (in particular hydrogen and helium), where they form classical two-dimensional Coulomb systems. Apart from studying the intrinsic properties of these nearly ideal systems, like the transition from an electron gas to a Wigner solid, one can use the electrons also as a sensitive probe to investigate the surface of quantum liquids and solids. The examples presented here include the surface of solid H₂, He films, and the interface between liquid and solid He, where phenomena such as annealing, layering, and crystal growth are studied. In addition, the interaction between the electrons and long-wavelength interfacial modes leads to an electrohydrodynamic instability, which bears interesting similarities with other critical phenomena.     

Volumetric ultrasound system for left ventricle motion imaging

An external ultrasound oscillating probe has been developed for the purpose of visualizing dynamically the left cardiac ventricle three-dimensional (3D) movements and deformations. The fundamental principle of this probe is to maintain in continuous oscillation a classical one-dimensional (1D) transducer array around its axis at a maximum oscillation rate of 3 degrees per millisecond. A global medical system, including hardware elements and a software package, has been designed for this application. A motorization set and electronic boards enable this new oscillating probe to be used with any recent echograph equipped with a cardiac module and an external triggering cineloop. Moreover, in order to obtain 3D/4D left ventricle movements from a set of 2D recorded images, a rendering method based on the 2D discrete Fourier transform is applied. Promising preliminary results have been obtained on some patients, and a clinical study on a great number of subjects (both healthy and heart complaint people) was carried out.     

Adaptive reshaping of objects in (multiparameter) Hilbert space for enhanced detection and classification: an application of receiver operating curve statistics to laser-based mass spectroscopy

We propose a new approach to the classical detection problem of discrimination of a true signal of interest from an interferent signal, which may be applied to the area of chemical sensing. We show that the detection performance, as quantified by the receiver operating curve (ROC), can be substantially improved when the signal is represented by a multicomponent data set that is actively manipulated by means of a shaped laser probe pulse. In this case, the signal sought (agent) and the interfering signal (interferent) are visualized by vectors in a multidimensional detection space. Separation of these vectors can be achieved by adaptive modification of a probing laser pulse to actively manipulate the Hamiltonian of the agent and interferent. We demonstrate one implementation of the concept of adaptive rotation of signal vectors to chemical agent detection by means of strong-field time-of-flight mass spectrometry.     

Influence of high temperatures on a fiber-optic probe for temperature measurement

The use of optical fiber in a temperature probe or sensor for optical pyrometry in the 100-1000 °C range is affected by the low thermal stability of classical fibers. We have studied the different sources of perturbations induced by exposure to high temperature. Two specific fibers especially suited for a high-temperature environment were tested and compared. Low (100 °C/min) and very fast (100 °C/s) fiber heating was performed to evaluate its influence on the guided flux and the induced error on temperature measurement. The metallic-coated fiber shows a reproducible temperature error that can be predicted. This important result permits the development of an uncooled fiber probe for temperature monitoring in high-temperature environments such as aerospace engines.     

Routine femtogram-level chemical analyses using vibrational spectroscopy and self-cleaning scanning probe microscopy tips

Simultaneous structural and chemical characterization of materials at the nanoscale is both an immediate need and an ongoing challenge. This article reports a route to address this need, which can be rapidly adopted by practitioners, by combining the benefits of widely available scanning probe microscopy and vibrational microspectrometry. In an atomic force microscope (AFM), the probe tip can provide a nanoscale topographic image. Here, we use a temperature-controlled probe tip to selectively acquire an analyte from a specified location and determine its mass in a thermogravimetric manner. The tip is then analyzed via complementary Raman and Fourier transform infrared microspectrometers, providing a molecular characterization of samples down to the femtogram level in minutes. The probe can be self-cleaned and employed for repeated use by rapidly heating it to vaporize the analyte. By combining the established analytical modalities of AFM and vibrational spectrometry, a complete physical and molecular characterization of nanoscale domains is possible: mass determination is facile, thermal analyses can be integrated on the probe, and the obtained spectral data can be related to existing knowledge bases.     

Mass spectrometric inverse gas chromatography: investigation of polymeric phase transitions

An improved inverse gas chromatographic method involving the use of a mass-specific detector for the determination of the glass transition temperature of polymeric materials is described. The new method allows the use of several probe solutes simultaneously with an automated, closed-loop injector and stepped temperature programming. The result is a single continuous chromatogram for each probe solute over a range of temperatures encompassing the glass transition temperature, T(g). Several different methods for the exact determination of T(g) from the chromatogram were investigated, including the classical van't Hoff-type plots with retention volumes calculated from both the peak maximum and first moment values of the elution peaks. Two new methods are also proposed for the evaluation of T(g) from either the temperature dependence of the second moments of the elution peaks for probe solutes or simple inspection of the variation of elution peak height (width) with temperature. All four methods for the determination of T(g) are evaluated with three probe solutes and four different polymers, viz., poly(methyl methacrylate), poly(ethylene terephthalate), polycarbonate, and two batches of polystyrene with different molecular weights and T(g) values. Three phenomenological models were used to interpret the chromatographic retention mechanisms of the solute probes in glassy and rubbery polymers. These are (i) the classical adsorption/absorption model for glass and rubber polymers, (ii) the single absorption mechanism model, and (iii) a dual-mode model previously used to explain the sorption of gases, such as CO(2), in glassy polymers. It is concluded that no single approach is adequate to interpret the experimental results for all of the systems, although each model is adequate for some individual solute/polymer combinations.     

Field enhancement in apertureless near-field scanning optical microscopy.

The near field of an apertureless near-field scanning optical microscopy probe is investigated with a multiple-multipole technique to obtain optical fields in the vicinity of a silicon probe tip and a glass substrate. The results demonstrate that electric field enhancements of >15 relative to the incident fields can be achieved near a silicon tip, implying intensity enhancements of several orders of magnitude. This enhancement arises both from the antenna effect of the elongated probe and from a proximity effect when the probe is near the substrate surface and its image dipoles play a role.     

Multilevel Effects in a Driven Generalized Rabi Model

We study numerically the onset of higher-level excitations and resonance frequency shifts in the generalized multilevel Rabi model with dispersive coupling under strong driving. The response to a weak probe is calculated using the Floquet method, which allows us to calculate the probe spectrum and extract the resonance frequency. We test our predictions using a superconducting circuit consisting of a transmon coupled capacitively to a coplanar waveguide resonator. This system is monitored by a weak probe field and at the same time driven at various powers by a stronger microwave tone. We show that the transition from the quantum to the classical regime is accompanied by a rapid increase of the transmon occupation and consequently that the qubit approximation is valid only in the extreme quantum limit.     

量热探针在热等离子射流测量中的应用

为了测量等离子射流的温度和速度,设计了量热探针测量系统,采用补偿式的量热法来测量热等离子体 的比焓得到热等离子体的温度;也可作为水冷皮托管来测量射流的动压头确定射流流速。系统采用Φ0.8 mm探 针实际测量最高温度达8515K。根据等离子喷枪的输入功率和热效率估算出喷枪出口处射流的温度和速度,与探 针的测量结果比较吻合。     

Analytic model of the current-voltage characteristic of a small probe in a magnetic field

An analytic model is proposed for a small wall probe (whose dimensions perpendicular to the magnetic field are smaller than the ion Larmor radius) in a completely ionized plasma. The structure of the current collection regions is described and an analytic expression is obtained for the current-voltage characteristic of the probe. It is shown that a model with a classical diffusion coefficient gives results close to the experimental values. Pis’ma Zh. Tekh. Fiz. 24, 1–10 (November 26, 1998)     

Strategic use of affinity-based mass spectrometry techniques in the drug discovery process.

Advances in biomolecular mass spectrometry (Bio-MS) have made this technique an invaluable tool for analytical chemists and biochemists alike. The applicability of Bio-MS approaches in drug discovery now encompasses in vitro, cellular, and in vivo pharmacological and clinical applications in an unprecedented expansion of utility. As a result, the role of Bio-MS in pharmaceutical discovery continues to proliferate for both structural and functional characterization of biomolecules. From target characterization to lead optimization, affinity techniques have been used to purify, probe, and enrich analytes of interest. Affinity selection employed prior to MS analysis can "edit" out extraneous noise and enable the researcher to examine only what is important. These affinity-based methods can be used as an alternative strategy when classical biochemical techniques are insufficient in advancing difficult projects. We have applied various affinity techniques in conjunction with mass spectrometry throughout the drug discovery process. This perspective will describe affinity-based mass spectrometry methodologies and related concepts, illustrated with original results.     

颤抖自动补偿式微型精密加工仪的设计

设计了一种在精密加工操作中对操作人员及外界非正常颤抖信号进行检测并自动补偿的微型操作仪。仪器结构精巧,具有可拆卸及更换的加工探头,可满足不同精密加工的使用需求。基于经典PID闭环控制和边缘检测原理,采用激光干涉仪对精密加工位置信号进行检测,对干扰信号进行判断并做出相应补偿措施;采用压电陶瓷微电动机PM的逆向运动自动补偿颤抖产生的误差,保证精密加工的可靠性和精确度。实验表明,该微型仪器能自动补偿颤抖干扰信号,精度可达到1μm,对精密加工的精度提高及误差补偿研究有一定借鉴价值。     

Plate bending analysis using the classical or the Reissner–Mindlin models

Plates can be solved with the classical or the Reissner–Mindlin plate model using the same computer code with an appropriate treatment of the direct boundary element formulation. A field decomposition is employed to establish a connection between these plate models and to obtain a boundary element formulation for the classical model from that used for the Reissner–Mindlin one. The classical model is related to the irrotational component of the field related to the rotations of the plate. The use of this field component in both the fundamental solution and the direct boundary integral equation of the Reissner–Mindlin model carries the classical model approach. Furthermore, the well-known fundamental solution derived from the classical model can be employed as the irrotational field of the fundamental solution of the Reissner–Mindlin model. In this way, the fundamental solution used by Danson to perform classical analysis was used as the irrotational component and the obtained results were compared with those obtained with the well-known Weeën's formulation.     

Scanning electrochemical cell microscopy: theory and experiment for quantitative high resolution spatially-resolved voltammetry and simultaneous ion-conductance measurements

Scanning electrochemical cell microscopy (SECCM) is a high resolution electrochemical scanning probe technique that employs a dual-barrel theta pipet probe containing electrolyte solution and quasi-reference counter electrodes (QRCE) in each barrel. A thin layer of electrolyte protruding from the tip of the pipet ensures that a gentle meniscus contact is made with a substrate surface, which defines the active surface area of an electrochemical cell. The substrate can be an electrical conductor, semiconductor, or insulator. The main focus here is on the general case where the substrate is a working electrode, and both ion-conductance measurements between the QRCEs in the two barrels and voltammetric/amperometric measurements at the substrate can be made simultaneously. In usual practice, a small perpendicular oscillation of the probe with respect to the substrate is employed, so that an alternating conductance current (ac) develops, due to the change in the dimensions of the electrolyte contact (and hence resistance), as well as the direct conductance current (dc). It is shown that the dc current can be predicted for a fixed probe by solving the Nernst-Planck equation and that the ac response can also be derived from this response. Both responses are shown to agree well with experiment. It is found that the pipet geometry plays an important role in controlling the dc conductance current and that this is easily measured by microscopy. A key feature of SECCM is that mass transport to the substrate surface is by diffusion and, for charged analytes, ion migration which can be controlled and varied quantifiably via the bias between the two QRCEs. For a working electrode substrate this means that charged redox-active analytes can be transported to the electrode/solution interface in a well-defined and controllable manner and that relatively fast heterogeneous electron transfer kinetics can be studied. The factors controlling the voltammetric response are determined by both simulation and experiment. Experiments demonstrate the realization of simultaneous quantitative voltammetric and ion conductance measurements and also identify a general rule of thumb that the surface contacted by electrolyte is of the order of the pipet probe dimensions.     

Surface imaging using holographic optical tweezers

We present an imaging technique using an optically trapped cigar-shaped probe controlled using holographic optical tweezers. The probe is raster scanned over a surface, allowing an image to be taken in a manner analogous to scanning probe microscopy (SPM), with automatic closed loop feedback control provided by analysis of the probe position recorded using a high speed CMOS camera. The probe is held using two optical traps centred at least 10 μm from the ends, minimizing laser illumination of the tip, so reducing the chance of optical damage to delicate samples. The technique imparts less force on samples than contact SPM techniques, and allows highly curved and strongly scattering samples to be imaged, which present difficulties for imaging using photonic force microscopy. To calibrate our technique, we first image a known sample--the interface between two 8 μm polystyrene beads. We then demonstrate the advantages of this technique by imaging the surface of the soft alga Pseudopediastrum. The scattering force of our laser applied directly onto this sample is enough to remove it from the surface, but we can use our technique to image the algal surface with minimal disruption while it is alive, not adhered and in physiological conditions. The resolution is currently equivalent to confocal microscopy, but as our technique is not diffraction limited, there is scope for significant improvement by reducing the tip diameter and limiting the thermal motion of the probe.     

Efficient atom localization via probe absorption in an inverted-Y atomic system

The behaviour of atom localization in an inverted-Y atomic system is theoretically investigated. For the atoms interacting with a weak probe field and several orthogonal standing-wave fields, their position information can be obtained by measuring the probe absorption. Compared with the traditional scheme, we couple the probe field to the transition between the middle and top levels. It is found that the probe absorption sensitively depends on the detuning and strength of the relevant light fields. Remarkably, the atom can be localized at a particular position in the standing-wave fields by coupling a microwave field to the transition between the two ground levels.     

四发射单接收光学非接触测头

研究开发了一种具有4个发射光源和1个CCD摄像机作为接收装置的光学非接触测头．测头可以用来测量包括具有强反射表面的曲面．测头基于三角法工作原理．在恰当设计的情况下,至多只有1路从工件表面反射回来的光,能够进入CCD摄像机．通过将相应通道切断,很容易消除镜面反射光的影响．这时测头就相当于1个三发射单接收光学非接触测头．测头可以同时用来测量表面的位置和方向．对于具有很大倾斜的表面具测头仍能正常工作,采用干涉滤光片消除了环境光的影响．提出了一种系统的标定方法．通过对量块的测量证实了系统工作的正确性和有效性并给出了实验结果．