Improvements to the Tendon-Actuated Lightweight In-Space MANipulator (TALISMAN)

Devices for manipulating and precisely placing payloads are critical for efficient space operations including berthing of spacecraft, in-space assembly, construction and repair. Key to the success of many NASA space activities has been the availability of long-reach crane-like devices such as the Shuttle Remote Manipulation System (SRMS) and the Space Station Remote Manipulation System (SSRMS). These devices have been used for many operations including berthing visiting spacecraft to the International Space Station, deployment of spacecraft, space station assembly, astronaut positioning, payload transfer, and spacecraft inspection prior to atmospheric re-entry. Retiring the Space Transportation System has led to the removal of the SRMS from consideration for in-space missions, thus creating a capability gap. Recognizing this gap, work was initiated at NASA on a new architecture for long-reach space manipulators. Most current devices are constructed by joining revolute joints with carbon composite tubes, with the joints accounting for the majority of the device mass. For example in the case of the SRMS, the entire device mass is 410 kg (904 lbm); the joint structure, motors, gear train, cabling, etc., accounts for the majority of the system mass because the carbon composite tubes mass is 46 kg (101 lbm). An alternate space manipulator concept, the Tendon-Actuated Lightweight In-Space MANipulator (TALISMAN) was created to address deficiencies in the current state-of-the-art in long-reach manipulators. The antagonistic tendon actuated joint architecture allows the motors actuating the joint to be removed from the joint axis, which simplifies the joint design while simultaneously providing mechanical advantage for the motors. The improved mechanical advantage, in turn, reduces the size and power requirements for the motor and gear train. This paper will describe recent architectural improvements to the TALISMAN design that: 1) improve the operational robustness of the system by enabling maneuvers not originally possible by varying the TALISMAN geometry; 2) enable efficient active antagonistic control of a joint while sharing cable between antagonistic tension networks; and 3) uses a unique arrangement of differential capstans to reduce motor torque requirements by an order of magnitude. The paper will also summarize recent efforts to enable autonomous deployment of a TALISMAN including the deployment concept of operations and associated hardware system design. The deployment forces are provided by the same motor systems that are used for articulation, thus reducing the mass associated with the deployment system. The deployment approach is being tested on a TALISMAN prototype which is designed to provide the same operational performance as a shuttle-class manipulator. The prototype has been fabricated and is operational in a new facility at NASA Langley Research Center that has a large area (15.2 m by 21.3 m [50 ft by 70 ft]) air-bearing floor

Cytomegalovirus (CMV) Disease Despite Weekly Preemptive CMV Strategy for Recipients of Solid Organ and Hematopoietic Stem Cell Transplantation

BACKGROUND: Transplant recipients presenting with cytomegalovirus (CMV) disease at the time of diagnosis of CMV DNAemia pose a challenge to a preemptive CMV management strategy. However, the rate and risk factors of such failure remain uncertain. METHODS: Solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT) recipients with a first episode of CMV polymerase chain reaction (PCR) DNAemia within the first year posttransplantation were evaluated (n = 335). Patient records were reviewed for presence of CMV disease at the time of CMV DNAemia diagnosis. The distribution and prevalence of CMV disease were estimated, and the odds ratio (OR) of CMV disease was modeled using logistic regression. RESULTS: The prevalence of CMV disease increased for both SOT and HSCT with increasing diagnostic CMV PCR load and with screening intervals >14 days. The only independent risk factor in multivariate analysis was increasing CMV DNAemia load of the diagnostic CMV PCR (OR = 6.16; 95% confidence interval, 2.09–18.11). Among recipients receiving weekly screening (n = 147), 16 (10.8%) had CMV disease at the time of diagnosis of CMV DNAemia (median DNAemia load 628 IU/mL; interquartile range, 432–1274); 93.8% of these cases were HSCT and lung transplant recipients. CONCLUSIONS: Despite application of weekly screening intervals, HSCT and lung transplant recipients in particular presented with CMV disease at the time of diagnosis of CMV DNAemia. Additional research to improve the management of patients at risk of presenting with CMV disease at low levels of CMV DNAemia and despite weekly screening is warranted

Theory for the electromigration wind force in dilute alloys

A multiple scattering formulation for the electromigration wind force on atoms in dilute alloys is developed. The theory describes electromigration via a vacancy mechanism. The method is used to calculate the wind valence for electromigration in various host metals having a close-packed lattice structure, namely aluminum, the noble metals copper, silver and gold and the $4d$ transition metals. The self-electromigration results for aluminum and the noble metals compare well with experimental data. For the $4d$ metals small wind valences are found, which make these metals attractive candidates for the experimental study of the direct valence.Comment: 18 pages LaTeX, epsfig, 8 figures. to appear in Phys. Rev. B 56 of 15/11/199

Prostate-specific antigen testing accuracy in community practice

BACKGROUND: Most data on prostate-specific antigen (PSA) testing come from urologic cohorts comprised of volunteers for screening programs. We evaluated the diagnostic accuracy of PSA testing for detecting prostate cancer in community practice. METHODS: PSA testing results were compared with a reference standard of prostate biopsy. Subjects were 2,620 men 40 years and older undergoing (PSA) testing and biopsy from 1/1/95 through 12/31/98 in the Albuquerque, New Mexico metropolitan area. Diagnostic measures included the area under the receiver-operating characteristic curve, sensitivity, specificity, and likelihood ratios. RESULTS: Cancer was detected in 930 subjects (35%). The area under the ROC curve was 0.67 and the PSA cutpoint of 4 ng/ml had a sensitivity of 86% and a specificity of 33%. The likelihood ratio for a positive test (LR+) was 1.28 and 0.42 for a negative test (LR-). PSA testing was most sensitive (90%) but least specific (27%) in older men. Age-specific reference ranges improved specificity in older men (49%) but decreased sensitivity (70%), with an LR+ of 1.38. Lowering the PSA cutpoint to 2 ng/ml resulted in a sensitivity of 95%, a specificity of 20%, and an LR+ of 1.19. CONCLUSIONS: PSA testing had fair discriminating power for detecting prostate cancer in community practice. The PSA cutpoint of 4 ng/ml was sensitive but relatively non-specific and associated likelihood ratios only moderately revised probabilities for cancer. Using age-specific reference ranges and a PSA cutpoint below 4 ng/ml improved test specificity and sensitivity, respectively, but did not improve the overall accuracy of PSA testing

Simplicity in Visual Representation: A Semiotic Approach

Simplicity, as an ideal in the design of visual representations, has not received systematic attention. High-level guidelines are too general, and low-level guidelines too ad hoc, too numerous, and too often incompatible, to serve in a particular design situation. This paper reviews notions of visual simplicity in the literature within the analytical framework provided by Charles Morris' communication model, specifically, his trichotomy of communication levels—the syntactic, the semantic, and the pragmatic. Simplicity is ultimate ly shown to entail the adjudication of incompatibilities both within, and between, levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68281/2/10.1177_105065198700100103.pd

Cumulative prostate cancer risk assessment with the aid of the free-to-total prostate specific antigen ratio.

OBJECTIVE: To evaluate the cumulative risk of having a prostate cancer diagnosis in a repeated screening situation in relation to the free-to-total prostate specific antigen ratio (F/T-PSA). PATIENTS AND METHODS: The present study includes 1385 men (aged 50-70 years) who underwent prostate biopsy for the first time in the screening program that started in 1995. In case of a benign finding, the men have been followed biennially and new biopsies performed in case of persistently elevated PSA. The cumulative risk to be diagnosed with prostate cancer until July 1, 2002 was calculated by the Kaplan-Meier method and comparison was made between different levels of T-PSA and F/T-PSA ratios. RESULTS: Of 2129 biopsies 469 showed cancer. The cumulative 5-year risk to be diagnosed with prostate cancer was significantly dependent of the F/T-ratio. The risk for men with a T-PSA of 3-5.99 g/ml was 16% [6-25%] for those who had a ratio of >30% and 44% [34-60%] for those with a ratio of <10%. The corresponding difference for patients with a T-PSA of 6-9.99 g/ml was even more pronounced: 21% [0-42%] vs. 80% [64-96%]. CONCLUSION: By completing the T-PSA measurement with the F/T-PSA ratio it is possible to significantly better assess the cumulative prostate cancer risk within the next five years (without the aid of further urological work-up)

Characteristics of screening detected prostate cancer in men 50 to 66 years old with 3 to 4 ng./Ml. Prostate specific antigen

Purpose: We defined the yield and nature of prostate cancer in the setting of population based, randomized prostate specific antigen (PSA) guided screening in men with PSA levels between 3 and 4 ng./ml. who were 50 to 65 years old at the time of randomization. Materials and Methods: Sextant biopsies were performed in 243 men with PSA of 3 to 4 ng./ml. Therapy decisions were based on core cancer length, histological grade and life expectancy. Results: Of the men 32 (13.2%) had prostate cancer constituting 23% of all of the 137 prostate cancers to date detected in the first round of our screening study. Age and PSA were similar in men with and without prostate cancer. Men with prostate cancer had significantly lower free PSA and free-to-total PSA ratio, and higher PSA density. Cancer was clinical stage T1c in 27 cases and stage T2 in 5. Hypoechoic areas were noted at transrectal ultrasound in 10 cases. Digital rectal examination and transrectal ultrasound were normal in 21 cases (66%). To date 14 patients have undergone prostatectomy. Surgical specimens showed a mean tumor volume of 1.8 cc (range 0.6 to 4.4) and significant amounts of high grade tumor were present in only 3 cases. Margins were positive in 5 cases, and pathological stage was pT2 in 8 cases and pT3 in 6. Conclusions: By lowering the PSA cutoff from 4 to 3 ng./ml. an increase in cancer detection by 30% was achieved. While the addition of free-to-total ratio and PSA density may reduce the number of biopsies by about 15% with sensitivity maintained at 90%, systematic sextant biopsies were necessary in most of these men as 66% of the tumors were negative on transrectal ultrasound and digital rectal examination. The majority of these cancers were clinically significant and suitable for curative treatment. If therapy decisions are based on the pathological findings of the biopsies, the risk of treating insignificant cancers seems low