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A high-directivity combined self-beam/null-steering array for secure point-to-point binary phase-shift keying communications is introduced. The system provides high directivity and reduced probability of interception using just two antenna elements. Using quadrature phase-shift keying modulators allows for compact single-layer fabrication. The 2.4-GHz prototype is tested at interrogation angles of 0[degrees], -10[degrees], and +20[degrees], and demonstrates high signal-to-interference ratio directivity, completely disabling interception [+ or -]20[degrees] from the direction of the interrogator. The system should find various applications where secure communications are required. Index Terms--Digital communication, microwave receivers, phase conjugation, phased arrays, transponders. Digital Object Identifier 10.1109/TMTT.2007.895405

A full-duplex dual-frequency self-steering array using phase detection and phase shifting is presented. By RF decoupling the transmitter and receiver arrays, the proposed system promises greater system efficiency by ensuring a constant transmit power. This also allows for a separate low-frequency interrogating signal capable of various modulation schemes. A two-element prototype is demonstrated with interrogating and retrodirective frequencies of 1.425 and 2.85 GHz, respectively. Retrodirectivity is reported for angles of 0[degrees], -15[degrees], and +25[degrees]. The power of the received signal is improved by up to 12 dB for -60[degrees] [less than or equal to] [theta] < 60[degrees] when compared to a conventional two-element array. Index Terms--Antenna arrays, microwave antenna arrays, phased arrays, retrodirective array.

A 16-element two-dimensional (2-D) retrodirective array using self-oscillating mixers (SOMs) is presented. SOMs allow for easier implementation of larger 2-D arrays by eliminating the complex local-oscillator (LO) feed structure. A 4 x 4 element retrodirective array using SOMs is demonstrated at an LO frequency of 7.68 GHz. Each element is phased locked at the LO frequency with an accompanying RF frequency isolation of 17.9 dB between adjacent horizontal elements and 22.2 dB between adjacent vertical elements. A---10-dBm external injection-locking signal is applied to reduce the phase noise of the 16-element array to -68.2 dBc/Hz at 10-kHz offset. Retrodirectivity is observed in the [phi] = 0[degrees], [phi] = -45[degrees], and [phi] = -90 plane for scattering angles of [theta] = -15[degrees], [theta] = 0[degrees], and [theta] = +30[degrees]. Index Terms--Antenna arrays, beam steering, microwave antenna arrays, phased arrays, retrodirective array, self-oscillating mixer (SOM).

A wireless sensor server is developed based on a reconfigurable active smart-antenna/retrodirective array. The system can serve as both a retrodirective array transponder and a smart-antenna receiver simply by changing the frequency of the local oscillator applied to the mixers, enabling it to best utilize its hardware to suit its communication environment. When operating as a direct-conversion receiver, the receiver array successfully demodulates a quaternary phase-shift keying (QPSK) modulated signal with circuit gain of 7 dB and [E.sub.b]/[N.sub.O] for BER = [10.sup.-4] is approximately 12 dB without any error correction. In the retrodirective array mode, the system provides 20-dB circuit gain and 20-dB radio-frequency-intermediate-frequency isolation at the center frequency as well as phase conjugation, exhibiting excellent retrodirectivity. The mixers perform phase conjugation and modulation simultaneously, enabling the transmission of locally stored data. The local data is successfully extracted by an interrogator. Index Terms--Digital communication, microwave receivers, phase conjugation, phased arrays, transponders.

A retrodirective transponder based on a novel compact phase-conjugating mixer with conversion gain has been developed. The active circuit uses one port for both incoming and outgoing signals, enabling a reduction of circuit size, and the balanced structure provides suppression of undesired signals. By using a modulated local oscillator, the circuit can modulate the received signal in order to retransmit local information to the remote site. A microstrip antenna is integrated with the phase conjugator and the whole system was fabricated on a single substrate, enabling a one-card system. A four-element prototype array with 0.5 [[Lambda].sub.0] array spacing demonstrated excellent measured retrodirectivity. Additionally, a simplified binary-phase-shift-keying signal transmitted by the array is recovered successfully at the source location, demonstrating great potential for remote tagging and wireless sensor applications. Index Terms--Active integrated antenna, mobile communications, phase conjugator, retrodirective array, transponder.

A lo largo de la pasada década ha habido esfuerzos a nivel mundial, en todas las áreas médicas, para poder basar las decisiones clínicas en las pruebas disponibles según lo descrito por una revisión exhaustiva de la literatura. Las fracturas de cadera son un problema importante de salud a nivel mundial, con una incidencia anual de aproximadamente 1,7 millones. La media de edad de la población está aumentando en todo el mundo, y se espera que el número de fracturas de cadera se pueda triplicar en los próximos 50 años. Las tasas de mortalidad al cabo de un año oscilan actualmente entre el 14 y el 36%, y el cuidado de estos pacientes supone una gran carga económica a nivel mundial. Las opciones quirúrgicas para tratar las fracturas del cuello femoral están estrechamente vinculadas a los factores individuales del paciente y a la localización y el grado de desplazamiento de la fractura. El tratamiento no quirúrgico de las fracturas intracapsulares de cadera es limitado. Basándonos en una revisión crítica y basada en la evidencia de la bibliografía, hemos encontrado unas diferencias mínimas entre los diversos implantes empleados para la fijación interna de las fracturas desplazadas. La artroplastia unipolar cementada sigue siendo una buena opción con unos resultados razonables. Los resultados tras una prótesis total de cadera son favorables y parecen ser superiores a la fijación interna en un grupo apropiado de pacientes. [ABSTRACT FROM AUTHOR]

The diagnosis and treatment of patients who have both hip and lumbar spine pathologies may be a challenge because overlapping symptoms may delay a correct diagnosis and appropriate treatment. Common complaints of patients who have both hip and lumbar spine pathologies include low back pain with associated buttock, groin, thigh, and, possibly, knee pain. A thorough patient history should be obtained and a complete physical examination should be performed to identify the primary source of pain. Plain and advanced imaging studies and diagnostic injections can be used to further delineate the primary pathology and guide the appropriate sequence of treatment. Both the surgeon and the patient should understand that although one pathology is managed, management of the other pathology may be necessary because of persistent pain. The recognition of both entities may help reduce the likelihood of misdiagnosis, and the management of both entities in the appropriate sequence may help reduce the likelihood of persistent symptoms.

Various treatment options exist for distal radius fractures, and the complications associated with operative and nonoperative management are well documented in the literature. While surgical management with the use of various buttress and locked plating constructs has gained popularity, the long-term outcomes of these plating techniques have not yet significantly demonstrated improved outcomes, as compared to adequately reduced nonoperative measures. Furthermore, this operative technique can be associated with failures and complications. We present a case report of one volar-plate construct requiring revision, secondary to loss of fracture reduction, with no evidence of implant loosening or failure. A literature review on the complications associated with these plate constructs is also presented.

The Orthopaedic In-Training Examination (OITE) is a tool used by residency directors to evaluate a resident's fund of orthopedic knowledge. In this study, we correlated resident study habits and preparation tools with performance on the OITE. Data analysis indicated statistically significant correlations between successful OITE performance and frequent review of current orthopedic journals (Journal of Bone and Joint Surgery-American Edition, r = .6, P < .001; Journal of the American Academy of Orthopaedic Surgeons, r = .36, P = .02), daily orthopedic reading (r = .34, P = .03), increased preparation time for OITE (r = .31, P = .04), and more hours committed to studying (r = .37, P = .01). In addition, residents who emphasized prior OITEs and self-assessment examinations when preparing had higher scores (r = .53, P < .001, and r = .64, P < .001, respectively). Our study results show that several factors, including structured study habits and use of specific study materials, contribute to residents' successful OITE performance. Adaptation of these findings by current orthopedic residents may have a positive impact on OITE performance.

Purpose: We tested the hypothesis that the antiangiogenic activity of the type I interferons (IFNs), could affect tumor engraftment and growth in murine xenograft models of neuroblastoma., Methods: Subcutaneous and retroperitoneal human neuroblastoma xenografts were established in SCID mice. Five days after tumor cell inoculation, daily subcutaneous injections of human IFN-alpha at several different doses were initiated and continued for 30 days. The effectiveness of continuous delivery of low-dose interferon was then tested using a gene therapy approach in which an adeno-associated virus vector encoding IFN-beta (rAAV-IFN-beta) was used to mediate expression prior to retroperitoneal tumor implantation., Results: Subcutaneous and retroperitoneal tumors were significantly smaller in IFN-alpha-treated mice, as compared with control mice. Intratumoral basic fibroblast growth factor and vascular endothelial growth factor expression were also decreased, as was mean intratumoral endothelial cell density. Interestingly, the lower doses of IFN-alpha were more effective than the higher dose. No tumors developed in any of the mice given rAAV-IFN-beta, whereas each of the mice that received control vector developed large tumors., Conclusions: Treatment with IFN had a significant impact on neuroblastoma engraftment and growth in mice, particularly when delivered continuously using a gene therapy approach. This activity appears to be mediated in part by inhibition of tumor-induced angiogenesis through the downregulation of tumor-elaborated factors, including basic fibroblast growth factor and vascular endothelial growth factor., (Copyright 2004 Elsevier Inc.)