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An electronically tunable reflectarray element is proposed in this work to design beam-steering antennas useful for radar applications. A reduced size reflectarray unit cell is properly synthesized in order to extend the antenna beam scanning capabilities within a wider angular region. The radiating structure is accurately optimized to provide a full phase tuning range by adopting a single varactor load as phase shifter element. A 0.46λ-reflectarray cell is designed at the frequency of 11.5GHz, obtaining a phase agility of about 330°. The cell is successfully adopted for the design of a 21 X 21 reconfigurable reflectarray. The antenna is numerically tested for different configurations of the varactors capacitance values, and good beam-steering performances are demonstrated within a wide angular range. [ABSTRACT FROM AUTHOR]

Benzocyclobutene (BCB) polymer is proposed in this study as an innovative and versatile substrate material for millimetre-wave reflectarrays. The excellent material features in terms of low loss, low dielectric constant and strong dielectric stability against frequency and temperature are highlighted. The design, realisation and test of a 60 GHz reflectarray with 21×21 variable-sized patches giving a focused boresight beam pattern are fully described. The BCB thickness is chosen on the basis of a parametric analysis performed on the unit cell to optimise the performances in terms of dielectric losses and radiation bandwidth. The in-house fabrication process able to assemble multi-layered BCB substrates is described in detail. Experimental results on the radiation pattern and the boresight gain are used to validate both the synthesis and the manufacturing process. [ABSTRACT FROM AUTHOR]

An extensive analysis is performed on the aperture-coupled reflectarray configuration to highlight and quantify the bandwidth enhancement due to the use of reduced inter-element spacings. Bandwidth extension is directly evaluated on the phase curves relative to the reflection coefficient against frequency for different lengths of the tuning line. The operating frequency range computed with the proposed approach is numerically validated on the gain patterns of synthesized reflectarrays and a strong broadband behavior is demonstrated for reflectarrays of moderate aperture dimensions and reduced unit cell size. [ABSTRACT FROM AUTHOR]

The design of microstrip reflect arrays requires the use of a design curve to correlate the phase of the reradiated field and the size of the elements. In this Letter this parameter has been evaluated by analyzing the field scattered from an isolated reflect-array unit cell. As a test case a microstrip reflect array has been designed with the use of these data. Even if this approach neglects the mutual coupling effects, the measured reflect-array radiation pattern shows that the main beam steering agrees with the design requirements. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 411–414, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10479 [ABSTRACT FROM AUTHOR]

The effects of radiation emission on the dynamic development of a neon seeded dense plasma focus are observed. The radiative cooling of the discharge is found to be responsible for the >10 times the increase in density of the pinch. [ABSTRACT FROM AUTHOR]

Portal thrombosis is a rare complication of splenectomy. We performed 12 laparoscopic splenectomies and observed this complication only in one patient with idiopathic thrombocytopenia (ITP). The right branch of the portal vein presented a partial thrombosis, while the left branch was completely obstructed by thrombi. Abdominal ultrasonography and an ultrasound doppler exam allowed us to diagnose this event and a retrograde angiography performed afterward confirmed our diagnosis. A 48-h intravenous heparin treatment was promptly begun, followed by anticoagulant drugs (dicumarol). The patient was dismissed 5 days afterward, presenting a steady-state ultrasound doppler pattern and a complete normalization of liver parameters. An ultrasound doppler exam performed 1 month after anticoagulant therapy showed a complete resolution of portal thrombosis. We believe that early diagnosis of this rare complication, prompt beginning of anticoagulant therapy, and care in surgical procedures may reduce patient life-threatening risks and assure complete remission. [ABSTRACT FROM AUTHOR]

Portal thrombosis is a rare complication of splenectomy. We performed 12 laparoscopic splenectomies and observed this complication only in one patient with idiopathic thrombocytopenia (ITP). The right branch of the portal vein presented a partial thrombosis, while the left branch was completely obstructed by thrombi. Abdominal ultrasonography and an ultrasound doppler exam allowed us to diagnose this event and a retrograde angiography performed afterward confirmed our diagnosis. A 48-h intravenous heparin treatment was promptly begun, followed by anticoagulant drugs (dicumarol). The patient was dismissed 5 days afterward, presenting a steady-state ultrasound doppler pattern and a complete normalization of liver parameters. An ultrasound doppler exam performed 1 month after anticoagulant therapy showed a complete resolution of portal thrombosis. We believe that early diagnosis of this rare complication, prompt beginning of anticoagulant therapy, and care in surgical procedures may reduce patient life-threatening risks and assure complete remission. [ABSTRACT FROM AUTHOR]

The dispersive analysis of the x-ray continuum is employed to determine the electron temperature of a dense pinched plasma. A curved crystal spectrometer was used to obtain the desired dispersion, and two or more p-i-n (doubly diffused silicon) diodes were used to monitor the time-resolved emission. The dispersive technique is inherently more accurate than filtering techniques and simpler to implement than laser scattering techniques. In an experimental verification of the technique, the time-resolved temperature of a plasma focus pinch was measured under various conditions, and was found to be consistent with density observations and MHD calculations. It was possible to observe the cooling effect of radiation emission from seeded plasma focus discharges. The elliptical crystal spectrometer is shown to be well suited to the analysis of the x-ray emission from a pinched plasma source. [ABSTRACT FROM AUTHOR]

An aperture-coupled reflectarray element with a reduced inter-element spacing is proposed. Bandwidth improvements are demonstrated by a smooth and similar behaviour of the phase design curves when properly decreasing the unit cell size. Experimental validations are reported for the measured radiation patterns of two reflectarray propotypes with different element spacings. [ABSTRACT FROM AUTHOR]

A magnetically stabilized plasma focus with controlled modulations has been demonstrated for the first time. A 3-mm-diam plasma focus with two wiggler periods of 1 cm each was kept stable for about 30 ns. Similar configurations with shorter periods could be used as intense wigglers for short-wavelength free-electron lasers. [ABSTRACT FROM AUTHOR]

A reconfigurable aperture-coupled reflectarray element offering a continuous tuning of the reflection phase is presented. A single varactor load is demonstrated to be sufficient for a full tuning range. Experimental validations are reported for the measured reflection phase of an X-band reflectarray element. [ABSTRACT FROM AUTHOR]

Proposes the use of printed reflectarrays as planar scatterers for SAR interferometry. Application of a phase-only synthesis to obtain a scattered field in a prescribed direction; Simulation of a reflectarray working at EERS1/2 frequency to validate the method; Performance of measurements on a 10GHz size-reduced prototype.

The determination of the phase of the field scattered from microstrip patches is a key factor in the design of reflect-array antennas. Although the problem has been treated in a number of theoretical articles, an experimental characterization of a such an important parameter has never been considered. In this Letter an experimental study of the phase of the field reradiated from small arrays of patches is presented. As a result a diagram of the phase of the scattered field versus the size of the patches is obtained. Results have been compared with the ones obtained with a commercial MoM package. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 163–164, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10403 [ABSTRACT FROM AUTHOR]

To meet world power demands, the use of nuclear power must continue to grow as a safe, emission-free, reliable, and economical source of energy. However, at the rate waste is produced by the existing fleet of nuclear reactors in the US, new repository capacity equal to the statutory capacity of the yet-to-open Yucca Mountain would be needed about every 20 years. Therefore, the ability to expand, or even maintain the nuclear power capacity in the US will be limited, unless either additional disposal capacity is identified, or waste volume, proliferation risk, and toxicity dose are significantly reduced. A preferred option for the destruction (transmutation) of waste from reactors is based on the use of thermal modular helium reactor systems (MHRs). This paper gives a brief outline of the MHR-based transmutation concept and its attendant advantages. [ABSTRACT FROM AUTHOR]

In the Deep-Burn concept, destruction of the transuranic component of light water reactor (LWR) waste is carried out in one burn-up cycle, accomplishing the virtually complete destruction of weapons-usable materials (Plutonium-239), and up to 90% of all transuranic waste, including the near totality of Neptunium-237 (the most mobile actinide in the repository environment) and its precursor, Americium-241.Waste destruction would be performed rapidly, without multiple reprocessing of plutonium, thus eliminating the risks of repeated handling of weapons-usable material and limiting the generation of secondary waste. There appears to be no incentive in continuing the destruction of waste beyond this level.An essential feature of the Deep-Burn Transmuter is the use of ceramic-coated fuel particles that provide very strong containment and are highly resistant to irradiation, thereby allowing very extensive destruction levels (“Deep Burn”) in the one pass, using gas-cooled modular helium reactor (MHR) technology developed for high-efficiency energy production. The fixed moderator (graphite) and neutronically transparent coolant (helium) provide a unique neutron energy spectrum to cause Deep-Burn, and inherent safety features, specific to the destruction of nuclear waste, that are not found in any other design.Deep-Burn technology could be available for deployment in a relatively short time, thus contributing effectively to waste problem solutions. Extensive modeling effort has led to conceptual Deep-Burn designs that can achieve high waste destruction levels (70% in critical mode, 90% in with a supplemental subcritical step) within the operational envelope of commercial MHR operation, including long refueling intervals and the highly efficient production of energy (approximately 50%). To the plant operator, a Deep-Burn Transmuter will be identical to its commercial reactor counterpart. [Copyright &y& Elsevier]

Background: The incidence of complications resulting from fine-needle biopsy of adrenal masses in patients already treated by radical procedures for primitive neoplasms of the lungs and kidneys substantiates our opinion concerning laparoscopy as both a diagnostic and therapeutic procedure.Methods: We performed 70 laparoscopic adrenalectomies from April 1995 to December 1999. In five patients, the adrenal mass appeared at follow-up evaluation in patients submitted to surgery for a spinocellular lung cancer. One patient underwent surgery for renal adenocarcinoma. In two patients, the adrenal mass was present already at the time primitive lung tumor was diagnosed, so adrenalectomy was performed at the first lung surgery in one patient and 2 weeks before lung surgery in the other patient. All the patients were placed in a lateral position for a transperitoneal approach. Right adrenal masses were present in seven patients, whereas one patient had an adrenal mass in a left location.Results: No laparotomy was required. The average surgical time was 160 min. (range, 115-120 min). No morbility or mortality occurred, and the average hospital stay was 4 days (range, 3-11 days). All the patients had a complete removal of their masses, which averaged 4.5 cm (range, 2.5-6 cm) in size. Histology confirmed the metastatic origin of the mass in five of seven patients with primary lung cancer, and in one patient with previous kidney cancer. At this writing, three patients were disease free and still alive respectively at 3, 5, and 18 months. Three patients died of brain metastases respectively at 16, 36, and 36 months. An adenoma was proved in the other two cases.Conclusions: Laparoscopic adrenalectomy allows us to propose a much more aggressive approach to adrenal masses demonstrated at follow-up evaluation or in patients with primary lung or kidney cancer and no masses at other locations. Nevertheless a much larger study is required for definitive conclusions on a survival rate. We believe that a mini-invasive procedure such as laparoscopy may allow us to replace a rational surgical approach with a more certain pathologic diagnosis. [ABSTRACT FROM AUTHOR]

The incidence of complications resulting from fine-needle biopsy of adrenal masses in patients already treated by radical procedures for primitive neoplasms of the lungs and kidneys substantiates our opinion concerning laparoscopy as both a diagnostic and therapeutic procedure. We performed 70 laparoscopic adrenalectomies from April 1995 to December 1999. In five patients, the adrenal mass appeared at follow-up evaluation in patients submitted to surgery for a spinocellular lung cancer. One patient underwent surgery for renal adenocarcinoma. In two patients, the adrenal mass was present already at the time primitive lung tumor was diagnosed, so adrenalectomy was performed at the first lung surgery in one patients were placed in a lateral position for a transperitoneal approach. Right adrenal masses were present in seven patients, whereas one patient had an adrenal mass in a left location. No laparotomy was required. The average surgical time was 160 min. (range, 115–120 min). No morbility or mortality occurred, and the average hospital stay was 4 days (range, 3–11 days). All the patients had a complete removal of their masses, which averaged 4.5 cm (range, 2.5–6 cm) in size. Histology confirmed the metastatic origin of the mass in five of seven patients with primary lung cancer, and in one patient with previous kidney cancer. At this writing, three patients were disease free and still alive respectively at 3, 5, and 18 months. Three patients died of brain metastases respectively at 16, 36, and 36 months. An adenoma was proved in the other two cases. Laparoscopic adrenalectomy allows us to propose a much more aggressive approach to adrenal masses demonstrated at follow-up evaluation or in patients with primary lung or kidney cancer and no masses at other locations. Nevertheless a much larger study is required for definitive conclusions on a survival rate. We believe that a mini-invasive procedure such as laparoscopy may allow us to replace a rational surgical approach with a more certain pathologic diagnosis. [ABSTRACT FROM AUTHOR]