Telescope Technique Research Articles

Sub-Airy disk angular resolution with high dynamic range in the near-infrared

Lunar occultations (LO) are a simple and effective high angular resolution method, with minimum requirements in instrumentation and telescope time. They rely on the analysis of the diffraction fringes created by the lunar limb. The diffraction phenomen occurs in space, and as a result LO are highly insensitive to most of the degrading effects that limit the performance of traditional single telescope and long-baseline interferometric techniques used for direct detection of faint, close companions to bright stars. We present very recent results obtained with the technique of lunar occultations in the near-IR, showing the detection of companions with very high dynamic range as close as few milliarcseconds to the primary star. We discuss the potential improvements that could be made, to increase further the current performance. Of course, LO are fixed-time events applicable only to sources which happen to lie on the Moon’s apparent orbit. However, with the continuously increasing numbers of potential exoplanets and brown dwarfs beign discovered, the frequency of such events is not negligible. I will list some of the most favorable potential LO in the near future, to be observed from major observatories.

Enhancement of the Yakutsk array by atmospheric Cherenkov telescopes to study cosmic rays above 10<sup>15</sup> eV

The aim of the Yakutsk array enhancement project is to create an instrument to study the highest-energy galactic cosmic rays (CRs) -- their sources, energy spectrum, and mass composition. Additionally, there will be unique capabilities for investigations in the transition region between galactic and extragalactic components of CRs. Using the well-developed imaging atmospheric Cherenkov telescope technique adapted to the energy region $E>10^{15}$ eV, we plan to measure the longitudinal structure parameters of the shower, e.g., angular and temporal distributions of the Cherenkov signal related to $X_{max}$ and the mass composition of CRs. The main advantages of the Yakutsk array, such as its multi-component measurements of extensive air showers, and model-independent CR energy estimation based on Cherenkov light measurements, will be inherited by the instrument to be created.

Multiple harmonic ULF waves in the plasma sheet boundary layer observed by Cluster

The passage of the Cluster satellites in a polar orbit through Earth's magnetotail has provided numerous observations of harmonically related Pc 1–2 ULF wave events, with the fundamental near the local proton cyclotron frequency Ωcp. Broughton et al. (2008) reported observations by Cluster of three such events in the plasma sheet boundary layer, and used the wave telescope technique to determine that their wave vectors k were nearly perpendicular to B. This paper reports the results of a search for such waves throughout the 2003 Cluster tail passage. During the 4 month period of July–October 2003, 35 multiple‐harmonic wave events were observed, all in the plasma sheet boundary layer (PSBL). From the first observed event (22 July) to the last (28 October), 13 of Cluster's 42 tail passes had at least one event. The wave events were rather evenly distributed from XGSE = −7 RE out to the Cluster apogee distance of −18 RE, with one event observed at −4 RE. ZGSE for these events ranged from −10 to −3 RE and +3 to +7 RE (i.e., there were no events for ∣Z∣ < 3 RE). The wave events, with durations from ∼1 to 50 min, were consistently associated with signatures of the PSBL: elevated fluxes of counterstreaming ions with energies ranging from ∼3 to 30 keV, and elevated fluxes of electrons with energies ranging from 0.25 to ∼5 keV. Analysis of plasma parameters suggests that although waves occurred only when the ion beta exceeded 0.1 (somewhat larger than typical for the PSBL), ion particle pressure may be of more physical importance in controlling wave occurrence. Electron distributions were more isotropic in pitch angles than the ion distributions, but some evidence of counterstreaming electrons was detected in 83% of the events. The ions also showed clear signatures of shell‐like or ring‐like distributions; i.e., with reduced fluxes below the energy of maximum flux. The suprathermal ion fluxes were asymmetric in all events studied, with more ions streaming earthward (for events both north and south of the central plasma sheet). Good agreement between the observed frequency of the fundamental harmonic and the local Ωcp suggests that the waves were observed near the region of their origin and did not propagate along B, consistent with the wave telescope analysis.

Transcatheter closure of coronary artery fistula using the new Amplatzer vascular plug and a telescoping catheter technique

Coronary artery fistulas (CAFs) are rare congenital or acquired anomalies characterized by an abnormal communication between the coronary arteries and the cardiac chambers or great vessels. Most patients are asymptomatic during childhood but symptoms and complications have been reported with advancing age. Until recently, surgery was the routine mode of treatment for CAFs but, today transcatheter closure is recommended using a variety of devices, such as occlusion coils, vascular plugs, umbrella devices and covered stents. The case described here is of a 47-year-old woman with a large bilateral CAF draining into the pulmonary artery, successfully treated by implantation of two Amplatzer vascular plugs using a telescoping catheter technique.

Revision Total Hip Arthroplasty for a Vancouver Type B3 Periprosthetic Fracture Using an Allograft-Cemented Stem Composite by the Telescoping Technique

We describe a case of successful revision total hip arthroplasty for a Vancouver type B3 periprosthetic femoral fracture with extensive bone stock deficiency and osteoporotic diaphyseal bone. The femur was reconstructed with an allograft-cemented stem composite using a telescoping technique and a drainage hole for surplus cement. This procedure facilitated stable stem fixation to the host femur without cement interference and bony fusion between the allograft and host bone, as revealed by bone scintigraphy. This technique provides a surgical option for a severe periprosthetic femoral fracture in which the femoral diaphyseal bone is too osteoporotic to support the fixation of an allograft-cementless stem composite.

Renal artery intervention

Renal artery stenosis may cause or deteriorate arterial hypertension and/or renal insufficiency. Technical improvements of diagnostic and interventional endovascular tools have led to a more widespread use of endoluminal renal artery revascularisation and extension of the indications for this type of therapy. The first renal artery balloon angioplasties were performed by Felix Mahler in Berne and Andreas Gruentzig in Zurich in 19771,2. Until the beginning of the 1990’s balloon angioplasty was the only method of percutaneous treatment of renal artery stenosis (RAS). Results were satisfying for stenoses caused by fibro-muscular dysplasia and atherosclerotic stenosis of the renal artery trunk, but limited for ostial atherosclerotic lesions, the most common manifestation of renal artery stenosis3,4. The introduction of stenting has revolutionised percutaneous renal revascularisation. Following promising single centre reports, two randomised studies proved the superiority of stenting over conventional balloon angioplasty3,5 in the treatment of atherosclerotic ostial renal artery stenosis. Nowadays using pre-mounted low profile stent devices atherosclerotic RAS can be treated successfully in almost all cases with restenosis rates ranging from 0 to 23% depending on the diameter of the renal artery5-9. Even if the recent randomised STAR and ASTRAL trials10,11 did not show any benefit of renal artery stenosis revascularisation over medical therapy there is nonetheless evidence that stenting of haemodynamically relevant atherosclerotic renal artery stenosis has an impact on blood pressure control, renal function, and left ventricular hypertrophy. A proper patient selection and a safe interventional technique are the key elements of a clinically successful outcome of the patient following the procedure. In particular, patients with a short history of deterioration of renal function might have the largest benefit from intervention. In patients with an advanced stage of renal failure the indication for stenting of atherosclerotic renal artery stenosis must be determined individually for each patient considering the overall prognosis. The online version of this manuscript introduces step-bystep into interventional treatment techniques for renal artery stenoses, from the simple guiding catheter technique to the modified “no-touch” technique (Figure 1a-e) or the telescope technique to access renal arteries with steep angulations from the femoral artery.

Magnetic energy distribution in the four‐dimensional frequency and wave vector domain in the solar wind

We present a measurement of the energy distribution in the four‐dimensional (4‐D) frequency and wave vector domain of magnetic field fluctuations in the solar wind. The measurement makes use of the wave telescope technique that has been developed particularly for multispacecraft data analysis. We review briefly the theoretical background and then present a numerical test using synthetic data; the technique is then applied to magnetic field data obtained while the Cluster spacecraft was in the solar wind. The energy distribution is determined in the flow rest frame in the frequency range below 0.2 rad/s and the wave number range below 0.0015 rad/km, corrected for the Doppler shift. We find the following properties in the energy distribution in the rest frame: (1) a double anisotropy in the wave vector domain associated with the mean magnetic field and the flow directions, (2) a symmetric distribution with respect to the sign of wave vector, and (3) no evidence for a linear dispersion relation in the frequency and wave number domain. Since the flow direction in the analyzed time interval is close to the normal direction to the bow shock, the anisotropy may well be associated with the bow shock. These results suggest that the solar wind is in a state of well‐developed strong turbulence and justifies the theoretical picture of quasi‐two‐dimensional turbulence that obtains in the presence of a (relatively) strong DC magnetic field. However, the fluctuations are not axisymmetric around the mean field and the energy distribution is extended in the perpendicular direction to the flow or shock normal. Anisotropy associated with the boundary is reminiscent of previously reported magnetosheath turbulence. This study opens a way to investigate solar wind turbulence in the full 4‐D frequency and wave vector space.

Is the Near-Earth Current Sheet Prior to Reconnection Unstable to Tearing Mode?

The tearing mode instability plays a key role in the triggering process of reconnection. The triggering collisionless tearing mode instability has been theoretically and numerically analyzed by many researchers. However, due to the difficulty in obtaining the observational wave number, it is still unknown whether the tearing mode instability can be excited in an actual plasma sheet prior to reconnection onset. Using the data from four Cluster satellites prior to a magnetospheric reconnection event on 13 September 2002, we utilized the wave telescope technique to obtain the wave number which corresponds to the peak of power spectral density. The wavelength is about 18RE and is consistent with previous theoretic and numerical results. After substituting the wave vector and other necessary parameters of the observed current sheet into the triggering condition of tearing mode instability, we find that the near-Earth current sheet prior to reconnection is unstable to tearing mode.

Spectral flux of the p-7Li(C) Q-M neutron source measured by proton recoil telescope

The cyclotron-based fast neutron source at NPI produces mono-energetic neutron fields up to 35 MeV neutron energy using the p + 7Li(carbon backing) reactions. To be applied for activation cross-section measurements, not only the intensity of neutron peak, but also the contribution of low-energy continuum in the spectra must be well determined. Simulations of the spectral flux from present source at a position of irradiated samples were performed using CYRIC TOF-data validated in the present work against LA150h by calculations with the transport Monte Carlo code MCNPX.Simulated spectra were tested by absolute measurements using a proton-recoil telescope technique. The recoil-proton spectrometer consisted of a shielded scattering chamber with polyethylene and carbon radiators and the ΔE1-ΔE2-E telescope of silicon-surface detectors located to the neutron beam axis at 45° in the laboratory system. Si-detectors were handled by usual data acquisition system. Dead-time – and pulse-overlap losses of events were determined from the count rate of pulse generator registered during duty cycle of accelerator operation. The proton beam charge and data were taken in the list mode for later replay and analysis.The calculations for 7 Li(p,n) and 12 C(p,n) reactions reasonably reproduce CYRIC TOF neutron source spectra. The influence of neutron source set-up (proton beam dimensions, 7 Li-foil, carbon stopper, cooling medium, target support/chamber and the geometry-arrangement of irradiated sample) on the spectral flux is discussed in details.

ULF Waves Associated with Solar Wind Deceleration in the Earth's Foreshock

Characteristics of ULF waves associated with the solar wind deceleration in the Earth's foreshock on 6–7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63 mHz. The wave vector in the GSE coordinates is estimated to be κ = (−4.29, 2.28, 1.21) × 10−4 km−1. In the solar wind frame, the frequency of waves becomes −9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.

Bronchial Complications Following Lung Transplantation

Introduction Bronchial complications owing to the airway anastomosis in lung transplantation are important causes of morbidity and mortality. They occur in up to 27% of cases as defined by stenosis, necrosis, and dehiscence. Treatment depends on the type of complication. Objective To report our experience to treat this complication. Methods Between 2000 and 2007, we performed 71 lung transplants of which 36 were bilateral. The total number of anastomoses was 107:52 to the right and 55 to the left. The telescoping technique was initially used (14 initial unilateral transplants), and after October, 2003 it was changed to an end-to-end anastomosis (57 transplants and 93 anastomoses). Results Eight patients developed bronchial complications including two that were bilateral. There were 4 stenosis, 3 dehiscences, and 3 necrosis complications (9.4%). The complication rate for telescoping anastomosis was 21.4%, and for the end-to-end technique, 7.5%. The treatment of the stenosis used metallic or plastic self-expandable stents. Two bronchial dehiscences resulted in case of bronchopleural fistulae, empyema, and death; the other patient experienced spontaneous resolution. Concerning bronchial necrosis, 1 patient developed fistulization to the pulmonary artery and massive hemoptysis, and the other with bilateral necrosis, a spontaneous resolution. Conclusion Our bronchial anastomosis complication rate was comparable with that in other reports. The rate for the telescoping technique was greater compared with the end-to-end technique. The treatment of bronchial stenosis with a self-expandable prosthesis showed good results.

One-Shot Versus Metal Telescopic Dilation Technique for Tract Creation in Percutaneous Nephrolithotomy: Comparison of Safety and Efficacy

The aim of this study was to assess the feasibility and morbidity of single-step acute dilation, named "one-shot" technique, including a single dilation of the nephrostomy tract with a 28F or 30F Amplatz dilator compared with metal telescopic dilation technique. Two hundred fourteen patients who underwent percutaneous nephrolithotomy (PNL) for stone disease from September 2005 to October 2007 were included in the study, and they were randomly divided into two groups according to the type of tract dilation technique: in group 1 (112 patients), Alken telescopic dilators were used; in group 2 (102 patients), one-shot technique was used. Access tract dilation time, X-ray exposure time, success rate, and blood loss and other complications were evaluated. One-shot technique was compared using Alken telescopic dilators without an increase in morbidity and with significant reduction in X-ray exposure (p = 0.003). There was no significant difference in the procedural success rate between groups 1 and 2 (100% v 96.07%, respectively) (p = 0.765). There was no any significant difference in complications. Access time was similar in both groups (p = 0.14). One-shot dilation was proved to be safe and effective like metal telescopic dilation even in patients with a history of ipsilateral open renal surgery. In this procedure, X-ray exposure is lower.

Statistical analysis of ground based magnetic field measurements with the field line resonance detector

Abstract. In this paper we introduce the field line resonance detector (FLRD), a wave telescope technique which has been specially adapted to estimate the spectral energy density of field line resonance (FLR) phase structures in a superposed wave field. The field line resonance detector is able to detect and correctly characterize several superposed FLR structures of a wave field and therefore constitutes a new and powerful tool in ULF pulsation studies. In our work we derive the technique from the classical wave telescope beamformer and present a statistical analysis of one year of ground based magnetometer data from the Canadian magnetometer network CANOPUS, now known as CARISMA. The statistical analysis shows that the FLRD is capable of detecting and characterizing superposed or hidden FLR structures in most of the detected ULF pulsation events; the one year statistical database is therefore extraordinarily comprehensive. The results of this analysis confirm the results of previous FLR characterizations and furthermore allow a detailed generalized dispersion analysis of FLRs.

The wave surveyor technique for fast plasma wave detection in multi-spacecraft data

Abstract. Multi-satellite missions like Cluster allow to study the full spatio-temporal variability of plasma processes in near-Earth space, and both the frequency and the wave vector dependence of dispersion relations can be reconstructed. Existing wave analysis methods include high-resolution beamformers like the wave telescope or k-filtering technique, and the phase differencing approach that combines the correlations measured at pairs of sensors of the spacecraft array. In this paper, we make use of the eigendecomposition of the cross spectral density matrix to construct a direct wave identification method that we choose to call the wave surveyor technique. The analysis scheme extracts only the dominant wave mode but is much faster to apply than existing techniques, hence it is expected to ease survey-type detection of waves in large data sets. The wave surveyor technique is demonstrated by means of synthetic data, and is also applied to Cluster magnetometer measurements.

Percutaneous Nephrolithotomy in Patients with Previous Open Nephrolithotomy: One-Shot versus Telescopic Technique for Tract Dilatation

Percutaneous nephrolithotomy (PCNL) can be done in patients who have previously had open nephrolithotomy. Currently, dilatation of the nephrostomy tract is achieved using an Amplatz renal dilator or telescopic metal dilators in these patients. The aim of this study was to compare the safety and efficacy of the "one-shot" procedure in patients with previous open nephrolithotomy with those of the current telescopic technique. Thirty-one patients with past history of open surgery for kidney stone disease underwent PCNL at our institution from February 2006 to March 2007. Patients were randomly divided into two groups according to dilation technique used: group A (telescopic procedure) and group B (one-shot procedure). X-ray exposure, blood loss, and complications were evaluated. No significant difference in hemoglobin decrease was seen in the two groups. The stone-free and complication rates were the same in the two groups. Fluoroscopy time during the one-shot procedure was significantly shorter than that of the telescopic procedure (P < 0.000). Our experience indicated that the one-shot procedure is feasible in patients with previous open nephrolithotomy. It is as safe and effective as the telescopic procedure, with significant reduction in x-ray exposure.

Low frequency wave sources in the outer magnetosphere, magnetosheath, and near Earth solar wind

Abstract. The interaction of the solar wind with the Earth magnetosphere generates a broad variety of plasma waves through different mechanisms. The four Cluster spacecraft allow one to determine the regions where these waves are generated and their propagation directions. One of the tools which takes full advantage of the multi-point capabilities of the Cluster mission is the wave telescope technique which provides the wave vector using a plane wave representation. In order to determine the distance to the wave sources, the source locator – a generalization of the wave telescope to spherical waves – has been recently developed. We are applying the source locator to magnetic field data from a typical traversal of Cluster from the cusp region and the outer magnetosphere into the magnetosheath and the near Earth solar wind. We find a high concentration of low frequency wave sources in the electron foreshock and in the cusp region. To a lower extent, low frequency wave sources are also found in other magnetospheric regions.

Natural limit on the γ/hadron separation for a stand alone air Cherenkov telescope

The γ/hadron separation in the imaging air Cherenkov telescope technique is based on differences between images of a hadronic shower and a γ induced electromagnetic cascade. One may expect for a large telescope that a detection of hadronic events containing Cherenkov light from one γ subcascade only is possible. In fact, simulations show that for the MAGIC telescope their fraction in the total protonic background is about 1.5% to 5.2% depending on the trigger threshold. It has been found that such images have small sizes (mainly below 400 photoelectrons) which correspond to the low energy primary γ's (below 100 GeV). It is shown that parameters describing shapes of images from one subcascade have similar distributions to primary γ events, so those parameters are not efficient in all methods of γ selection. Similar studies based on MC simulations are presented also for the images from 2γ subcascades which are products of the same π0 decay. The ratio of the number of the expected background from false γ and one π0 to the number of the triggered high energy photons from the Crab direction has been estimated for images with a small alpha parameter to show that the occurrence of this type of protonic shower is the reason for the difficulties with true γ selection at low energies.

Accuracy and utility of three-dimensional contrast-enhanced magnetic resonance angiography in planning carotid stenting

Contrast-enhanced magnetic resonance angiography (CE-MRA) is a proven diagnostic tool for the evaluation of carotid stenosis; however, its utility in planning carotid artery stenting (CAS) has not been addressed. This study assessed the accuracy of three-dimensional CE-MRA as a noninvasive screening tool, compared with digital subtraction angiography (DSA), for evaluating carotid and arch morphology before CAS. In a series of 96 CAS procedures during a 2-year period, CE-MRAs and DSAs with complete visualization from the aortic arch to the intracranial circulation were obtained before CAS in 60 patients. Four additional patients, initially considered potential candidates for CAS, were also evaluated with CE-MRA and DSA. The two-by-two table method, receiver operating characteristic curve, and Bland-Altman analyses were used to characterize the ability of CE-MRA to discriminate carotid and arch anatomy, suitability for CAS, and degree of carotid stenosis. The sensitivity and specificity of CE-MRA were, respectively, 100% and 100% to determine CAS suitability, 87% and 100% to define aortic arch type, 93% and 100% to determine severe carotid tortuosity, and 75% and 98% to detect ulcerated plaques. CE-MRA had 87% sensitivity and 100% specificity for the detection of carotid stenosis >/=80%. The accuracy of CE MRA to determine optimal imaging angles and stent and embolic protection device sizes was >90%. The operative technique for CAS was altered because of the findings of preoperative CE-MRA in 22 procedures (38%). The most frequent change in the operative plan was the use of the telescoping technique in 11 cases (18%). CAS was aborted in four patients (5%) due to unfavorable anatomy identified on CE-MRA, including prohibitive internal carotid artery tortuosity (n = 1), long string sign of the internal carotid artery (n = 2), and concomitant intracranial disease (n = 1). Among patients considered suitable for CAS by CE-MRA, technical success was 100%, and the 30-day stroke/death rate was 1.6%. Contrast-enhanced magnetic resonance angiography of the arch and carotid arteries is accurate in determining suitability for CAS and may alter the operative technique. Certain anatomic contraindications for CAS may be detected without DSA. Although CE-MRA is less accurate to estimate the degree of stenosis, it can accurately predict imaging angles, and stent and embolic protection device size, which may facilitate safe and expeditious CAS.

Brave new universe: illuminating the darkest secrets of the cosmos

Cosmologists yearn to behold the unseen elements of our universe. And as new technologies become more powerful and precise, scientists are getting their wisha though these tools are challenging the limits of our imagination as fast as they are answering many longstanding questions. Space is one of the last great frontiers for modern man. A never-ending source of investigation and inspiration, it beckons to scientists with an irresistible sirena (TM)s call. And in this glorious age of cosmology, astronomical measurement has never been more precise. The power provided to us by extraordinary new observational mechanisms has shattered former suppositions and stimulated exciting new visions of the universe. Using modern instruments such as the Wilkinson Microwave Anisotropy Probe (WMAP), astronomers now have access to information about the age and composition of the universe. By providing greatly improved answers, high-resolution satellite data and novel telescopic techniques have transformed one of sciencea (TM)s most speculative fields into a triumph of meticulous and rigorous detection. Yet as the technological tools grow increasingly robust and we are able to see farther and know more, we find that we have even more questions. Could there be realms beyond ordinary space? Might time, space, and matter simply be illusions? What unique blend of cosmological factors influences life on Earth? Featuring interviews with leaders in the field as well as thought-provoking descriptions of their work, Brave New Universe is a guided tour of current advances and controversies in cosmology.

Risk factors for airway complications within the first year after lung transplantation

Lung transplantation (LTx) has enjoyed increasing success with better survival in recent years. Nevertheless, airway anastomotic complications (AC) are still a potential cause of early morbidity and mortality. In this retrospective cohort study we looked at possible predictors of AC within the first year after LTx. Between July 1991 and December 2004, 232 consecutive single (n=102) and bilateral (n=130) LTx were performed (142 males and 90 females; mean age: 48 years [range 15-66 years]). Indications for LTx were emphysema (n=113), pulmonary fibrosis (n=45), cystic fibrosis (n=35), pulmonary hypertension (n=10), sarcoidosis (n=7) and miscellaneous (n=22). Donor variables (age, gender, PaO(2)/FiO(2), mechanical ventilation, ischemic time and preservation solution) and recipient variables (age, diagnosis, length, gender, pre-operative steroids, smoking, cytomegalovirus matching, LTx type, anastomotic type, wrapping and bypass) were evaluated in an univariate and multivariate model. Fifty-seven complications occurred in 362 airway anastomoses (15.7%) of which 55 (15.2%) within the first year after transplantation. Six patients died as a result of AC (mortality 2.6%) during the first year after LTx. In a univariate analysis (321 airway anastomoses at risk), anastomotic type (7/17 [Telescoping] vs 48/304 [End-to-end]; p=0.011), recipient length (p=0.0012), donor ventilation (>50-70h<; p=0.0015) and recipient male gender (43/191 [M] vs 12/130 [F]; p=0.0092) were significant predictors of AC. Three factors remained significant predictors in the multivariate analysis: telescoping technique (p=0.0495), recipient length (p=0.0029) and donor ventilation (p=0.003). Tall recipients and those receiving lungs from donors with prolonged ventilation have an increased risk to develop bronchial anastomotic problems. An end-to-end anastomosis should be preferred. Airway complications remain a matter of concern after lung transplantation.