The construction of a micro-pattern gas detector of dimensions
40×10
cm
2
is described. Two gas electron multiplier foils (GEM) provide the internal amplification stages. A two-layer readout ...structure was used, manufactured using the same technology as the GEM foils. The strips of each layer cross at an effective crossing angle of 6.7° and have a
406
μm
pitch. The performance of the detector has been evaluated in a muon beam at CERN using a silicon telescope as reference system. The position resolutions of two orthogonal coordinates are measured to be
50
μm
and
1
mm
, respectively. The muon detection efficiency for two-dimensional space points reaches 96%.
We report on the performance of a large micro-pattern detector with two gas electron multiplier foils and a two-layer readout structure at ground potential. The two readout layers each have a
406
μm
...pitch and cross at an effective angle of 6.7°. This structure allows for two orthogonal coordinates to be determined. Using a muon beam at CERN together with a silicon tracking system, the position resolutions of the two coordinates are measured to be
50
μm
and 1
mm respectively (1 standard deviation). The muon detection efficiency for the two-dimensional space points reaches 96%. The detector was found to be well operational over a wide range in the settings of the different electrical fields.
Lorentz angle measurements in silicon detectors Bartsch, V.; de Boer, W.; Bol, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2002, Letnik:
478, Številka:
1
Journal Article
Recenzirano
Odprti dostop
In this paper we study the Lorentz angles of both electrons and holes in magnetic fields up to
8
T and temperatures between 77 and
300
K. This is done before and after irradiating a detector with 21
...MeV protons up to a fluence of 10
13/cm
2, which is equivalent to ≈2.8×10
13/cm
2 1
MeV neutrons.
A small series production of detector modules made of MicroStrip Gas Counters (MSGC) and a Gas Electron Multiplier (GEM) foil has been exposed to a high-intensity hadron beam. We report about the ...reproductibility and stability of the detector responses and about the occurrence and consequences of discharges in the detector. The interdependence of the four voltage differences used in the detector has been studied by simulation and with X-ray measurements. Rate dependence of the signal amplitude is observed. The behaviour of the MSGC+GEM is compared to that of a state-of-the-art MSGC. Influence of various parameters on the detector response is investigated.
Future experiments are using silicon detectors in a high radiation environment and in high magnetic fields. The radiation tolerance of silicon improves by cooling it to temperatures of approximately
...130
K
. Charge carriers generated in silicon by traversing particles are deflected due to the Lorentz force. We present measurements of the Lorentz angle in irradiated silicon detectors between 77 and
300
K
. These results and the ones obtained from non-irradiated detectors are compared with simulations.
A system of detector modules consisting of a large size Gas Electron Multiplier (GEM), coupled to Micro Strip Gas Counters (MSGC), has been exposed to a pion beam at the Paul Scherrer Institute ...Cyclotron facility. As part of a CMS tracker milestone, the aim of this test was to investigate the robustness of such detectors when exposed to experimental conditions close to what is expected at the Large Hadron Collider (LHC) of CERN. Eighteen detector modules have been operated at voltage settings corresponding to 98% detection efficiency for Minimum Ionizing Particles during a period of 5 weeks. Sparking rates and strip losses have been monitored throughout the exposure. An operation margin of at least a factor of three with respect to the required gas gain has been demonstrated.
Amyotrophic lateral sclerosis is a devastating motor neuron disease and to this day not curable. While 5–10% of patients inherit the disease (familiar ALS), up to 95% of patients are diagnosed with ...the sporadic form (sALS). ALS is characterized by the degeneration of upper motor neurons in the cerebral cortex and of lower motor neurons in the brainstem and spinal cord. The wobbler mouse resembles almost all phenotypical hallmarks of human sALS patients and is therefore an excellent motor neuron disease model. The motor neuron disease of the wobbler mouse develops over a time course of around 40 days and can be divided into three phases: p0, presymptomatic; p20, early clinical; and p40, stable clinical phase. Recent findings suggest an essential implication of the NAD
+
-producing enzyme Nmnat2 in neurodegeneration as well as maintenance of healthy axons. Here, we were able to show a significant downregulation of both gene and protein expression of Nmnat2 in the spinal cord of the wobbler mice at the stable clinical phase. The product of the enzyme NAD
+
is also significantly reduced, and the values of the reactive oxygen species are significantly increased in the spinal cord of the wobbler mouse at p40. Thus, the deregulated expression of Nmnat2 appears to have a great influence on the cellular stress in the spinal cord of wobbler mice.
Abstract Background The objective of this study was to investigate primary stability of the proximal femoral nailing antirotation for the indication of unstable medial femoral neck fractures. The ...device was compared to the dynamic hip screw blade, which is a “gold standard” in the treatment of proximal femoral fractures. Methods Six pairs of human cadaver femurs were tested in a cyclic loading model with loads up to 200 N, 400 N, 600 N, 800 N, and 1000 N, respectively. Iliotibial tract was simulated by a chain that applied forces on the greater trochanter during loading. In vitro combined axial and bending loads were applied. Angular displacements during loading were recorded in all directions, and loads to failure were recorded. Findings For the cyclic loading test no statistically significant differences between the two groups could be detected. Specimens fixed with the dynamic hip screw blade showed higher displacements in the varus direction at 400 N and 600 N, in the external rotation at 200 N, 400 N and 600 N, and in the anterior direction at 400 N. Load to failure revealed no statistical difference between the two implants. Interpretation The proximal femoral nailing antirotation achieves primary stability comparable to the dynamic hip screw blade. The proximal femoral nailing antirotation combines the biomechanical favorable concept of intramedullary fixation with a minimally invasive surgical technique, which theoretically may be advantageous in clinical use. Further biomechanical studies are required to clarify to what extent the results of the present study can be transferred to the clinical situation.
Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease in humans and remains to have a fatal prognosis. Recent studies in animal models and human ALS patients indicate that ...increased reactive oxygen species (ROS) play an important role in the pathogenesis. Considering previous studies revealing the influence of ROS on mitochondrial physiology, our attention was focused on mitochondria in the murine ALS model, wobbler mouse. The aim of this study was to investigate morphological differences between wild-type and wobbler mitochondria with aid of superresolution structured illumination fluorescence microscopy, TEM, and TEM tomography. To get an insight into mitochondrial dynamics, expression studies of corresponding proteins were performed. Here, we found significantly smaller and degenerated mitochondria in wobbler motor neurons at a stable stage of the disease. Our data suggest a ROS-regulated, Ox-CaMKII-dependent Drp1 activation leading to disrupted fission-fusion balance, resulting in fragmented mitochondria. These changes are associated with numerous impairments, resulting in an overall self-reinforcing decline of motor neurons. In summary, our study provides common pathomechanisms with other ALS models and human ALS cases confirming mitochondria and related dysfunctions as a therapeutic target for the treatment of ALS.
The importance of osteoporosis in proximal humerus fractures is well recognized. However, the local distribution of bone quality in the humeral head may also have a significant effect because it ...remains unclear in what quality of bone screws of standard implants purchase. The goal of this study was to investigate whether the failure of proximal humerus locked plating can be predicted by the DensiProbe (ARI, Davos, Switzerland). A 2-part fracture with metaphyseal impaction was simulated in 12 fresh-frozen human cadaveric humeri. Using the DensiProbe, local bone quality was determined in the humeral head in the course of 6 proximal screws of a standard locking plate (Philos; Synthes GmbH, Solothurn, Switzerland). Cyclic mechanical testing with increasing axial loading until failure was performed. Bone mineral density (BMD) significantly correlated with cycles until failure. Head migration significantly increased between 1000 and 2000 loading cycles and significantly correlated with BMD after 3000 cycles. DensiProbe peak torque in all screw positions and their respective mean torque correlated significantly with the BMD values. In 3 positions, the peak torque significantly correlated with cycles to failure; here BMD significantly influenced mechanical stability. The validity of the DensiProbe was proven by the correlation between its peak torque measurements and BMD. The correlation between the peak torque and cycles to failure revealed the potential of the DensiProbe to predict the failure of locked plating in vitro. This method provides information about local bone quality, potentially making it suitable for intraoperative use by allowing the surgeon to take measures to improve stability.
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