Development of a Philips cryo-TEM provided with a liquid helium cooled tilt stage and a vacuum transfer system

1998 ◽  
Vol 4 (S2) ◽  
pp. 400-401
Author(s):  
R. Wagner ◽  
A.F. de Jong ◽  
A.G. Koster ◽  
R. Morrison ◽  
F. Tothill ◽  
...  
Keyword(s):  
High Resolution ◽  
Liquid Helium ◽  
Signal To Noise Ratio ◽  
Transfer System ◽  
Helium Temperature ◽  
Single Particles ◽  
Signal To Noise ◽  
Specimen Holder ◽  
2D Crystals ◽  
Beam Damage

In order to reduce beam damage, biological TEM specimens are often observed at temperatures close to the boiling point of liquid nitrogen (77 K). Recently, encouraging results on single particles as well as on 2D crystals have appeared, derived from images taken near liquid helium temperature (4 K), in dedicated TEMs. At these temperatures the high resolution frequencies are much better preserved, increasing the allowable dose and thus the signal to noise ratio.4 Here we present the design of a new dedicated Philips He-TEM which combines the full functionality of a CM300 TWIN with a vacuum transfer system and a liquid helium cooled specimen holder.A schematic overview of the Cryo-TEM is shown in figure 1. The key differences compared to a standard CM microscope are: 1) The tip of the specimen rod is cooled below 10 K and the rod itself cannot be taken out of the goniometer (CompuStage). 2) The specimen enters the column on the opposite side.

scholarly journals On cross-correlations, averages and noise in electron microscopy

2019 ◽  
Vol 75 (1) ◽  
pp. 12-18 ◽  
Author(s):  
Michael Radermacher ◽  
Teresa Ruiz
Keyword(s):  
High Resolution ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
3D Structure ◽  
Signal To Noise ◽  
High Resolution Structure ◽  
Multiple Copies ◽  
High Level ◽  
2D Images ◽  
Resolution Structure

Biological samples are radiation-sensitive and require imaging under low-dose conditions to minimize damage. As a result, images contain a high level of noise and exhibit signal-to-noise ratios that are typically significantly smaller than 1. Averaging techniques, either implicit or explicit, are used to overcome the limitations imposed by the high level of noise. Averaging of 2D images showing the same molecule in the same orientation results in highly significant projections. A high-resolution structure can be obtained by combining the information from many single-particle images to determine a 3D structure. Similarly, averaging of multiple copies of macromolecular assembly subvolumes extracted from tomographic reconstructions can lead to a virtually noise-free high-resolution structure. Cross-correlation methods are often used in the alignment and classification steps of averaging processes for both 2D images and 3D volumes. However, the high noise level can bias alignment and certain classification results. While other approaches may be implicitly affected, sensitivity to noise is most apparent in multireference alignments, 3D reference-based projection alignments and projection-based volume alignments. Here, the influence of the image signal-to-noise ratio on the value of the cross-correlation coefficient is analyzed and a method for compensating for this effect is provided.

Amendment to: Electron beam damage to organic specimens at liquid helium temperature

1983 ◽  
Vol 163 (3) ◽  
pp. 511 ◽  
Author(s):  
J. Lepault ◽  
J. Dubochet ◽  
I. Dietrich ◽  
E. Knapek ◽  
E. Zeitler
Keyword(s):  
Electron Beam ◽  
Liquid Helium ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Beam Damage

scholarly journals 53 Piscium, an SPB Star with Activity

2002 ◽  
Vol 185 ◽  
pp. 236-237
Author(s):  
J.-M. Le Contel ◽  
P. Mathias ◽  
E. Chapellier ◽  
J.-C. Valtier
Keyword(s):  
High Resolution ◽  
False Alarm ◽  
High Frequency ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Correlation Technique ◽  
Signal To Noise ◽  
Spectroscopic Observations ◽  
Auto Correlation ◽  
Frequency Variations

The star 53 Psc (HD 3379, B2.5IV) has been observed as variable by several authors (Sareyan et al., 1979) with frequencies around 10 c d–1 and has been classified as a β Cephei star. Conversely, other authors (e.g. Percy, 1971) found it to be constant.New high resolution, high signal-to-noise ratio, Spectroscopic observations have been performed at the Observatoire de Haute-Provence in 1996 over 11 nights. The spectral domain covers around 200 Å and is centered on Hδ. Radial velocities were deduced from an auto-correlation technique with a scatter around 0.4kms−1.No high frequency variations are observed. Three frequencies have been detected with a false alarm detection above the 1 % level. A fourth one may be present but its amplitude is below this 1 % level. Results are displayed in Table 1.

scholarly journals High-resolution coherency functionals for velocity analysis: An application for subbasalt seismic exploration

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. U53-U63 ◽  
Author(s):  
Andrea Tognarelli ◽  
Eusebio Stucchi ◽  
Alessia Ravasio ◽  
Alfredo Mazzotti
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Field Data ◽  
Signal To Noise Ratio ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
Velocity Analysis ◽  
Signal To Noise ◽  
Geologic Setting ◽  
Analytic Signals

We tested the properties of three different coherency functionals for the velocity analysis of seismic data relative to subbasalt exploration. We evaluated the performance of the standard semblance algorithm and two high-resolution coherency functionals based on the use of analytic signals and of the covariance estimation along hyperbolic traveltime trajectories. Approximate knowledge of the wavelet was exploited to design appropriate filters that matched the primary reflections, thereby further improving the ability of the functionals to highlight the events of interest. The tests were carried out on two synthetic seismograms computed on models reproducing the geologic setting of basaltic intrusions and on common midpoint gathers from a 3D survey. Synthetic and field data had a very low signal-to-noise ratio, strong multiple contamination, and weak primary subbasalt signals. The results revealed that high-resolution coherency functionals were more suitable than semblance algorithms to detect primary signals and to distinguish them from multiples and other interfering events. This early discrimination between primaries and multiples could help to target specific signal enhancement and demultiple operations.

scholarly journals Signal to Noise Ratio of APD-Based Monolithic Scintillator Detectors for High Resolution PET

2008 ◽  
Vol 55 (3) ◽  
pp. 842-852 ◽  
Author(s):  
M.C. Maas ◽  
D.R. Schaart ◽  
D.J. van der Laan ◽  
H.T. van Dam ◽  
J. Huizenga ◽  
...  
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Scintillator Detectors

scholarly journals 4.2 K sensitivity-tunable radio frequency reflectometry of a physically defined p-channel silicon quantum dot

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sinan Bugu ◽  
Shimpei Nishiyama ◽  
Kimihiko Kato ◽  
Yongxun Liu ◽  
Shigenori Murakami ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Radio Frequency ◽  
Liquid Helium ◽  
Signal To Noise Ratio ◽  
Matching Condition ◽  
Silicon On Insulator ◽  
Signal To Noise ◽  
Silicon Quantum Dot ◽  
Optimal Signal

AbstractWe demonstrate the measurement of p-channel silicon-on-insulator quantum dots at liquid helium temperatures by using a radio frequency (rf) reflectometry circuit comprising of two independently tunable GaAs varactors. This arrangement allows observing Coulomb diamonds at 4.2 K under nearly best matching condition and optimal signal-to-noise ratio. We also discuss the rf leakage induced by the presence of the large top gate in MOS nanostructures and its consequence on the efficiency of rf-reflectometry. These results open the way to fast and sensitive readout in multi-gate architectures, including multi qubit platforms.

scholarly journals The 12C/13C Ratio in Unevolved Cool Stars

1988 ◽  
Vol 132 ◽  
pp. 589-592
Author(s):  
Y. Chmielewski ◽  
D. L. Lambert
Keyword(s):  
High Resolution ◽  
Preliminary Analysis ◽  
Isotope Ratio ◽  
Signal To Noise Ratio ◽  
Carbon Isotope Ratio ◽  
High Signal ◽  
Reasonable Accuracy ◽  
Signal To Noise ◽  
Dwarf Stars ◽  
Cool Stars

We show that the carbon isotope ratio 12C/13C in the atmosphere of dwarf stars can be determined with reasonable accuracy from high resolution, high signal-to-noise ratio observations of the CH G-band in their spectra. Lines suitable for this purpose are selected from consideration of the solar case, for which 12C/13C = 89 is derived. A preliminary analysis of these features in the spectra of μ Her, δ Eri and τ Cet yields 12C/13C values of 84, 80 and 150 respectively.

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