| 1. |
- Gustafsson, U, et al.
(författare)
-
Compact fiber-optic fluorosensor using a continuous-wave violet diode laser and an integrated spectrometer
- 2000
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 71:8, s. 3004-3006
-
Tidskriftsartikel (refereegranskat)abstract
- A compact fluorosensor with a fiber-optic measurement probe was developed, employing a continuous-wave violet diode laser as an exciting source and an integrated digital spectrometer for the monitoring of fluorescence signatures. The system has the dimensions 22x13x8 cm(3), and features 5 nm spectral resolution and an excellent detectivity. Results from measurements on vegetation and human premalignant skin lesions are reported, illustrating the potential of the instrument. (C) 2000 American Institute of Physics. [S0034-6748(00)04508-1].
|
|
| 2. |
- Yakimov, V, et al.
(författare)
-
Electrostatic force-feedback force sensor incorporated in an ultrahigh vacuum force microscope
- 2000
-
Ingår i: Review of Scientific Instruments. - 0034-6748 .- 1089-7623. ; 71:1, s. 133-136
-
Tidskriftsartikel (refereegranskat)abstract
- A force sensor based on a fiber-optic interferometric displacement transducer incorporated in an ultrahigh vacuum atomic force microscope is described. The operation of the sensor is based on balancing the tip-sample interfacial force using an electrostatic actuator. The electrodes of the actuator are formed by the grounded W cantilever and the metallized end facet of the optical fiber used by the interferometer. Chemical reduction of Ag by a wet chemical method is used for metal coating of the fiber end. A special masking procedure is used to obtain a window hole in the metal coating at the position of the fiber core to allow for optical beam output. Using a window instead of a semitransparent metal film allows us to save the low-finesse characteristics of the interferometer which facilitates the calibration of cantilever displacement. The performance of the sensor is discussed and exemplified by experimental results from force-separation measurements on the W-Au system in ultrahigh vacuum. (C) 2000 American Institute of Physics. [S0034-6748(00)01401-5].
|
|
| 3. |
- Johansen, K, et al.
(författare)
-
Imaging surface plasmon resonance sensor based on multiple wavelengths : Sensitivity considerations
- 2000
-
Ingår i: Review of Scientific Instruments. - 0034-6748 .- 1089-7623. ; 71:9, s. 3530-3538
-
Tidskriftsartikel (refereegranskat)abstract
- A new, multiple wavelength surface plasmon resonance apparatus for imaging applications is presented. It can be used for biosensing, e.g., for monitoring of chemical and biological reactions in real time with label-free molecules. A setup with a fixed incident angle in the Kretschmann configuration with gold as the supporting metal is described, both theoretically and experimentally. Simulations of the sensor response based on independently recorded optical (ellipsometric) data of gold show that the sensitivity for three-dimensional recognition layers (bulk) increases with increasing wavelength. For two-dimensional recognition layers (adlayer) maximum sensitivity is obtained within a limited wavelength range. In this situation, the rejection of bulk disturbances, e.g., emanating from temperature variations, decreases, with increasing wavelength. For imaging surface plasmon resonance the spatial resolution decreases with increasing wavelength. Hence, there is always a compromise between spatial resolution, bulk disturbance rejection, and sensitivity. Most importantly, by simultaneously using multiple wavelengths, it is possible to maintain a high sensitivity and accuracy over a large dynamic range. Furthermore, our simulations show that the sensitivity is independent of the refractive index of the prism. (C) 2000 American Institute of Physics. [S0034-6748(00)02909-9].
|
|
| 4. |
- Johansson, M, et al.
(författare)
-
An equipment for three-dimensional spatially resolved gas analysis
- 2000
-
Ingår i: Review of Scientific Instruments. - 0034-6748 .- 1089-7623. ; 71:9, s. 3513-3521
-
Tidskriftsartikel (refereegranskat)abstract
- The apparatus described is able to measure three-dimensional temperature and partial pressure distributions in gas mixtures with a spatial resolution better than 0.5 mm. The measurements are performed in a well defined laminar gas flow in a duct of rectangular cross section. The gas mixture is sampled locally with a quartz tube orifice leak movable in three dimensions. Mass spectrometry is used for partial pressure measurements. The total pressure in the duct can be regulated in the range 50-760 Torr and the gas temperature can be varied between room temperature and 500 degrees C. The apparatus is primarily designed for studies of the distribution of reactants and products over catalytic surfaces. Because of the well defined gas flow in the duct the partial pressure distributions of reactants and products over the catalytic surface can be calculated with good accuracy. By comparing calculated pressure distributions to measured ones the local reaction rate on the catalytic surface as well as the pressures of reactants and products at the surface can be obtained. As an example it is shown how the hydrogen distribution over a platinum surface exposed to a mixture of hydrogen, oxygen, and argon can be used to calculate the local water formation rate on the platinum surface. (C) 2000 American Institute of Physics. [S0034-6748(00)01409-X].
|
|
| 5. |
- af Klinteberg, C, et al.
(författare)
-
Compact medical fluorosensor for minimally invasive tissue characterization
- 2005
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 76:3
-
Tidskriftsartikel (refereegranskat)abstract
- A compact fiber-optic point-measuring fluorosensor fully adapted to clinical studies is described. The system can use two excitation wavelengths, 337 and 405 nm, obtained from a nitrogen laser directly, or after dye laser conversion, respectively. The image intensifier used in the spectrometer can be gated with a variable time delay, allowing also time-resolved spectra to be extracted, with a time resolution of about 4 ns. Moreover, diffusely scattered white light can be spectrally recorded. The system is fully computer controlled enabling short recording times in clinical application, which are illustrated.
|
|
| 6. |
- Andersson, Mats, et al.
(författare)
-
Flexible lock-in detection system based on synchronized computer plug-in boards applied in sensitive gas spectroscopy
- 2007
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 78:11
-
Tidskriftsartikel (refereegranskat)abstract
- We present a flexible and compact, digital, lock-in detection system and its use in high-resolution tunable diode laser spectroscopy. The system involves coherent sampling, and is based on the synchronization of two data acquisition cards running on a single standard computer. A software-controlled arbitrary waveform generator is used for laser modulation, and a four-channel analog/digital board records detector signals. Gas spectroscopy is performed in the wavelength modulation regime. The coherently detected signal is averaged a selected number of times before it is stored or analyzed by software-based, lock-in techniques. Multiple harmonics of the modulation signal 1f, 2f, 3f, 4f, etc. are available in each single data set. The sensitivity is of the order of 10−5, being limited by interference fringes in the measurement setup. The capabilities of the system are demonstrated by measurements of molecular oxygen in ambient air, as well as dispersed gas in scattering materials, such as plants and human tissue.
|
|
| 7. |
- Andersson, M., et al.
(författare)
-
Using optical tweezers for measuring the interaction forces between human bone cells and implant surfaces: System design and force calibration
- 2007
-
Ingår i: Rev Sci Instrum. - : AIP Publishing. ; 78:7
-
Tidskriftsartikel (refereegranskat)abstract
- Optical tweezers were used to study the interaction and attachment of human bone cells to various types of medical implant materials. Ideally, the implant should facilitate cell attachment and promote migration of the progenitor cells in order to decrease the healing time. It is therefore of interest, in a controlled manner, to be able to monitor the cell adhesion process. Results from such studies would help foresee the clinical outcome of integrating medical implants. The interactions between two primary cell culture models, human gingival fibroblasts and bone forming human osteoblast cells, and three different implant materials, glass, titanium, and hydroxyapatite, were studied. A novel type of optical tweezers, which has a newly designed quadrant detector and a powerful 3 W laser was constructed and force calibrated using two different methods: one method in which the stiffness of the optical trap was obtained by monitoring the phase lag between the trap and the moved object when imposing a forced oscillation on the trapped object and another method in which the maximum trapping force was derived from the critical velocity at which the object escapes the trap. Polystyrene beads as well as cells were utilized for the calibrations. This is the first time that cells have been used directly for these types of force calibrations and, hence, direct measurements of forces exerted on cells can be performed, thus avoiding the difficulties often encountered when translating the results obtained from cell measurements to the calibrations obtained with reference materials. This more straightforward approach represents an advantage in comparison to established methods.
|
|
| 8. |
- Arnalds, U. B., et al.
(författare)
-
A magnetron sputtering system for the preparation of patterned thin films and in situ thin film electrical resistance measurements
- 2007
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 78:10, s. 103901-
-
Tidskriftsartikel (refereegranskat)abstract
- We describe a versatile three gun magnetron sputtering system with a custom made sample holder for in situ electrical resistance measurements, both during film growth and ambient changes on film electrical properties. The sample holder allows for the preparation of patterned thin film structures, using up to five different shadow masks without breaking vacuum. We show how the system is used to monitor the electrical resistance of thin metallic films during growth and to study the thermodynamics of hydrogen uptake in metallic thin films. Furthermore, we demonstrate the growth of thin film capacitors, where patterned films are created using shadow masks.
|
|
| 9. |
- Artemiev, A, et al.
(författare)
-
X-ray parabolic lenses made from glassy carbon by means of laser
- 2006
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 77:6
-
Tidskriftsartikel (refereegranskat)abstract
- Parabolic planar compound refractive lenses (CRLs) made from glassy carbon by means of laser ablation are presented. They have radii of curvatures of 5 and 200 mu m and geometric apertures of 40 and 900 mu m, respectively. The numbers of biconcave elements in the CRLs were 4, 7, and 200. The planar lenses allow formation of a linear focus of length comparable with the depths of their profiles. Usage of two CRLs in a crossed geometry provides formation of two-dimensional focus. The lenses were tested at the European Synchrotron Radiation Facility at the bending magnet beam line BM-5. The minimum experimental size of the focus has been achieved as 1.4 mu m.
|
|
| 10. |
- Attard, Phil, et al.
(författare)
-
Thermal calibration of photodiode sensitivity for atomic force microscopy
- 2006
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 77:11
-
Tidskriftsartikel (refereegranskat)abstract
- The photodiode sensitivity in the atomic force microscope is calibrated by relating the voltage noise to the thermal fluctuations of the cantilever angle. The method accounts for the ratio of the thermal fluctuations measured in the fundamental vibration mode to the total, and also for the tilt and extended tip of the cantilever. The method is noncontact and is suitable for soft or deformable surfaces where the constant compliance method cannot be used. For hard surfaces, the method can also be used to calibrate the cantilever spring constant.
|
|
