Spatial-frequency discrimination and detection: comparison of postadaptation thresholds

We found that inspecting a sine-wave grating elevated threshold for spatial-frequency discrimination as it does for contrast detection, but discrimination threshold was maximally elevated at about twice the adapting frequency, where detection threshold was little affected; and detection threshold was maximally elevated at the adapting frequency, where discrimination threshold was not elevated at all. Orientation tuning was roughly similar for contrast and for discrimination threshold elevations; elevations fell by half at between 7 and 17 deg from the adapting orientation. We compared our findings with the predictions of three models of discrimination: (1) The data are inconsistent with the idea that the most strongly stimulated channels are the most important channels for discrimination. (2) With an additional assumption, the Hirsch-Hylton scaled-lattice model could account for our finding that discrimination threshold elevations are asymmetric. (3) With no additional assumptions, the idea that discrimination is determined by the relative activities of multiple overlapping spatial-frequency channels or size-tuned neurons can account for our finding that discrimination thresholds are asymmetric. We propose a physiologically based discrimination model: Asymmetrically tuned cortical cells feed a ratio-tuned neural mechanism whose properties are formally analogous to those of ratio-tuned neurons that have recently been found in cat visual cortex. The linear relation between firing frequency and contrast can explain why discrimination threshold is substantially independent of contrast.     

The diagnostic utility of HASTE MRI in the evaluation of acute cholecystitis. Half-Fourier acquisition single-shot turbo SE

OBJECTIVE: To investigate the incidence of complications in the use of assisted reproductive technology in the management of infertile couples. DESIGN: Retrospective study. SETTING: The Egyptian IVF & ET Center, Maadi, Cairo, Egypt. PATIENT(S): Two thousand nine hundred twenty-four patients underwent IVF-ET or intracytoplasmic sperm injection (ICSI) in 3,500 cycles. INTERVENTION(S): IVF-ET, ICSI, ejaculate sperm, epididymal sperm aspiration, and testicular sperm extraction. MAIN OUTCOME MEASURE(S): Complications of the procedure and complications of pregnancy in 702 patients. RESULT(S): Fifteen hundred ovum pickups for IVF-ET and 2,000 ovum pickups for ICSI were performed. Clinical pregnancy occurred in 1,078 patients (30.8%). Four groups of complications were identified. Complications of the procedure occurred in 291 patients (8.3%). Complications of pregnancy included ectopic pregnancy in 1.9%, heterotopic pregnancy in 0.2%. abortion in 20.6%, multiple pregnancy in 28%, pregnancy-induced hypertension in 10%, preterm labor in 21.5%, low birth weight in 30.5%, and intrauterine death in 2%. Coincidental complications occurred in five patients (0.15%). Other complications that were difficult to measure included psychological breakdown and socioeconomic problems. CONCLUSION(S): Assisted reproductive technology is effective for the management of infertility and has an acceptable incidence of complications. Complications rarely endanger the life of the patient. When this line of treatment is offered, the indications should be definitive. Patients should be monitored properly and measures should be taken to minimize the incidence of complications.     

The Ultralight Steel Auto Body program completes phase I

The UltraLight Steel Auto Body program was initiated by the American Iron and Steel Institute and the International Iron and Steel Institute. The purpose of the program is to demonstrate the advantages of steel for reducing the weight of the automotive body-in-white. The holistic design approach—considering the body structure, materials, manufacturing methods, and engineering analysis together—has yielded a design for a body-in-white that is about 25 percent lighter than a typical vehicle produced at present, with improved structural performance. The materials and manufacturing processes required for the design are either in use or “near-reach” technologies.     

Radiographic patterns and associations of osteoarthritis of the knee in patients referred to hospital

OBJECTIVES: To investigate differing patterns and associations of osteoarthritis of the knee in patients referred to hospital. METHODS: Two hundred and fifty two consecutive patients (161 women, 91 men; mean age 70 years, range 34-91 years) referred to hospital with osteoarthritis of the knee underwent clinical, radiographic, and synovial fluid screening. RESULTS: Radiographic changes of osteoarthritis of the knee (definite narrowing with or without osteoarthritic features) were bilateral in 85% of patients. Of 470 knees affected, 277 (59%) were affected in two compartments and 28 (6%) in three compartments. Unilateral and isolated medial tibiofemoral osteoarthritis were more common in men. Calcium pyrophosphate crystal deposition was common (synovial fluid identification in 132 (28%) knees; knee chondrocalcinosis in 76 (30%) patients) and associated with disability, bilateral, multicompartmental and severe radiographic osteoarthritis, marked osteophytosis, attrition, and cysts. Multiple clinical nodes (58 (23%) patients) and radiographic polyarticular interphalangeal osteoarthritis (66 (26%) patients) were associated with a higher frequency of inactivity pain, disability, multicompartmental and severe radiographic change. Forestier's disease predominated in men but showed no other associations. CONCLUSIONS: In a group of patients referred to hospital osteoarthritis of the knee is usually bilateral and affects more than one compartment. Severe and multicompartmental radiographic changes are associated with calcium pyrophosphate crystal deposition, nodal change, and polyarticular interphalangeal osteoarthritis.     

Forskolin stimulation of water and cation permeability in aquaporin 1 water channels

Aquaporin 1, a six-transmembrane domain protein, is a water channel present in many fluid-secreting and -absorbing cells. In Xenopus oocytes injected with aquaporin 1 complementary RNA, the application of forskolin or cyclic 8-bromo- adenosine 3',5'-monophosphate increased membrane permeability to water and triggered a cationic conductance. The cationic conductance was also induced by direct injection of protein kinase A (PKA) catalytic subunit, reduced by the kinase inhibitor H7, and blocked by HgCl2, an inhibitor of aquaporin 1. The cationic permeability of the aquaporin 1 channel is activated by a cyclic adenosine monophosphate-dependent mechanism that may involve direct or indirect phosphorylation by PKA.     

Iodine-131-anti-B1 radioimmunotherapy for B-cell lymphoma

PURPOSE: The CD20 B-lymphocyte surface antigen expressed by B-cell lymphomas is an attractive target for radioimmunotherapy, treatment using radiolabeled antibodies. We conducted a phase I dose-escalation trial to assess the toxicity, tumor targeting, and efficacy of nonmyeloablative doses of an anti-CD20 monoclonal antibody (anti-B1) labeled with iodine-131 (131I) in 34 patients with B-cell lymphoma who had failed chemotherapy. PATIENTS AND METHODS: Patients were first given tracelabeled doses of 131I-labeled anti-B1 (15 to 20 mg, 5 mCi) to assess radiolabeled antibody biodistribution, and then a radioimmunotherapeutic dose (15 to 20 mg) labeled with a quantity of 131I that would deliver a specified centigray dose of whole-body radiation predicted by the tracer dose. Whole-body radiation doses were escalated from 25 to 85 cGy in sequential groups of patients in 10-cGy increments. To evaluate if radiolabeled antibody biodistribution could be optimized, initial patients were given one or two additional tracer doses on successive weeks, each dose preceded by an infusion of 135 mg of unlabeled anti-B1 one week and 685 mg the next. The unlabeled antibody dose resulting in the most optimal tracer biodistribution was also given before the radioimmunotherapeutic dose. Later patients were given a single tracer dose and radioimmunotherapeutic dose preceded by infusion of 685 mg of unlabeled anti-B1. RESULTS: Treatment was well tolerated. Hematologic toxicity was dose-limiting, and 75 cGy was established as the maximally tolerated whole-body radiation dose. Twenty-eight patients received radioimmunotherapeutic doses of 34 to 161 mCi, resulting in complete remission in 14 patients and a partial response in eight. All 13 patients with low-grade lymphoma responded, and 10 achieved a complete remission. Six of eight patients with transformed lymphoma responded. Thirteen of 19 patients whose disease was resistant to their last course of chemotherapy and all patients with chemotherapy-sensitive disease responded. The median duration of complete remission exceeds 16.5 months. Six patients remain in complete remission 16 to 31 months after treatment. CONCLUSION: Nonmyeloablative radioimmunotherapy with 131I-anti-B1 is associated with a high rate of durable remissions in patients with B-cell lymphoma refractory to chemotherapy.     

Creep mechanisms in beryllium

Observations of beryllium samples which have been creep tested between 922 K and 1422 K indicate that creep behavior is controlled by the relative strengths of the grain boundaries and the matrix. Since creep deformation can occur predominantly by grain boundary sliding or entirely by deformation within the grains, the creep strength was found to be controlled by the weaker of the two features. Low melting phases containing aluminum and silicon which formed along the grain boundaries acted as stress concentrations which favored localized grain boundary deformation, and recrystallization. Creep resistance was found to drop markedly when the BeO content was reduced substantially below 1 pct.     

Perceptual processes used by drivers during overtaking in a driving simulator

This study investigated the control strategies and decision making of drivers who were executing overtaking maneuvers in a fixed-base driving simulator. It was found that drivers were frequently inaccurate in deciding whether it was safe to overtake in front of an oncoming vehicle. One source of error in this situation was the control strategy adopted by the driver; in several instances our drivers initiated an overtaking maneuver when the oncoming car's distance was above a critical value, even though there was not sufficient time to complete a safe maneuver. Adaptation to closing speed (produced by driving on a straight open road) also had large effects on overtaking behavior. For all participants, closing speed adaptation resulted in decisions that were delayed, of higher risk, and more variable. Actual or potential applications of this research include improved training for younger drivers and the development of in-car interfaces that reduce closing speed adaptation.     

TV requirements for manipulation in space

An analytical and experimental study was conducted to specify a video system for remote manipulation in space. An operator function analysis identified two basic characteristics, work volume and element relationship, which define 4 manipulation tasks chosen for examination. A visual function analysis developed a set of elemental scene parameters which grouped the visual dimensions into major areas of influence. Simulation testing was conducted with a 4 degree-of-freedom motion frame which allowed an operator to perform the manipulation tasks. Four video systems were included in the simulation testing: a black and white and a color monoscopic system, a stereoscopic system, and a black and white 2-view system. A sequential experimental plan first provided an overall analysis of the effects of tasks, scene parameters and video systems. This was followed by a detailed experimental examination of the critical dimensions identified in the first experiment. Results are discussed in terms of a recommended TV system.