The Two Micron All Sky Survey (2MASS) Skrutskie, M. F; Cutri, R. M; Stiening, R ...
The Astronomical journal,
02/2006, Letnik:
131, Številka:
2
Journal Article
Recenzirano
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Between 1997 June and 2001 February the Two Micron All Sky Survey (2MASS) collected 25.4 Tbytes of raw imaging data covering 99.998% of the celestial sphere in the near-infrared J (1.25 mm), H (1.65 ...mm), and Ks (2.16 mm) bandpasses. Observations were conducted from two dedicated 1.3 m diameter telescopes located at Mount Hopkins, Arizona, and Cerro Tololo, Chile. The 7.8 s of integration time accumulated for each point on the sky and strict quality control yielded a 10 s point-source detection level of better than 15.8, 15.1, and 14.3 mag at the J, H, and Ks bands, respectively, for virtually the entire sky. Bright source extractions have 1 s photometric uncertainty of <0.03 mag and astrometric accuracy of order 100 mas. Calibration offsets between any two points in the sky are <0.02 mag. The 2MASS All-Sky Data Release includes 4.1 million compressed FITS images covering the entire sky, 471 million source extractions in a Point Source Catalog, and 1.6 million objects identified as extended in an Extended Source Catalog.
Structure elucidation is extremely important to understand and control processes in synthetic chemistry, in drug design, and in biomolecular function; and the most important step of structure ...elucidation is crystallization. Preceding crystallization of ionic compounds is usually ion-association in solution, which can be induced by a variety of ways. Here we study ion-association of hexaniobate and hexatantalate polyoxometalate salts in mixed water-alcohol solutions. These hexametalate clusters have the unusual characteristic of increased solubility with increased ion-association, which makes them ideal candidates to understand the fundamentals of ion-pairing. We utilize direct (X-ray scattering) and indirect (ion-conductivity) methods to document the ion-association as a function of alkali, concentration, alcohol:water ratio, and Nb versus Ta. The conductivity data coupled with X-ray scattering shows that decreasing solvent polarity increases cluster-alkali association; but decreases any interaction between the alkali-cluster aggregates. Conductivity data show the trend of increasing alkali-cluster association with increasing alkali size as is expected for hexaniobate, but has some discrepancies with hexatantalate. We attribute this to the concomitant effects of protonation of the clusters, with hexaniobate being a stronger base. These studies provide insight into aqueous behaviour of these clusters that exhibit the anomalous behaviour of high solubility with maximum ion-association.
To assess whether neonatal morbidities evident by the time of hospital discharge are associated with subsequent cerebral palsy (CP) or death.
This is a secondary analysis of data from a multicenter ...placebo-controlled trial of magnesium sulfate for the prevention of CP. The association between prespecified intermediate neonatal outcomes (
= 11) and demographic and clinical factors (
= 10) evident by the time of discharge among surviving infants (
= 1889) and the primary outcome of death or moderate/severe CP at age 2 (
= 73) was estimated, and a prediction model was created.
Gestational age in weeks at delivery (odds ratio OR: 0.74, 95% confidence interval CI: 0.67-0.83), grade III or IV intraventricular hemorrhage (IVH) (OR: 5.3, CI: 2.1-13.1), periventricular leukomalacia (PVL) (OR: 46.4, CI: 20.6-104.6), and male gender (OR: 2.5, CI: 1.4-4.5) were associated with death or moderate/severe CP by age 2. Outcomes not significantly associated with the primary outcome included respiratory distress syndrome, bronchopulmonary dysplasia, seizure, necrotizing enterocolitis, neonatal hypotension, 5-minute Apgar score, sepsis, and retinopathy of prematurity. Using all patients, the receiver operating characteristic curve for the final prediction model had an area under the curve of 0.84 (CI: 0.78-0.89). Using these data, the risk of death or developing CP by age 2 can be calculated for individual surviving infants.
IVH and PVL were the only neonatal complications evident at discharge that contributed to an individual infant's risk of the long-term outcomes of death or CP by age 2. A model that includes these morbidities, gestational age at delivery, and gender is predictive of subsequent neurologic sequelae.
· Factors known at hospital discharge are identified which are independently associated with death or CP by age 2.. · A model was created and validated using these findings to counsel parents.. · The risk of death or CP can be calculated at the time of hospital discharge..
The FAMA-NCS protocol is introduced for wireless LANs and ad-hoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMA-NCS (for floor acquisition ...multiple access with non-persistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMA-NCS is based on a three-way handshake between sender and receiver in which the sender uses non-persistent carrier sensing to transmit a request-to-send (RTS) and the receiver sends a clear-to-send (CTS) that lasts much longer than the RTS to serve as a "busy tone" that forces all hidden nodes to back off long enough to allow a collision-free data packet to arrive at the receiver. It is shown that carrier sensing is needed to support collision-free transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMA-NCS is analyzed for single-channel networks with and without hidden terminals; the analysis shows that FAMA-NCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulation experiments are used to confirm the analytical results. PUBLICATION ABSTRACT
Floor acquisition multiple access (FAMA) for packet-radio networks Fullmer, Chane L.; Garcia-Luna-Aceves, J. J.
Applications, Technologies, Architectures, and Protocols for Computer Communication: Proceedings of the conference on Applications, technologies, architectures, and protocols for computer communication; 28 Aug.-01 Sept. 1995,
10/1995
Conference Proceeding
Odprti dostop
A family of medium access control protocols for single-channel packet radio networks is specified and analyzed. These protocols are based on a new channel access discipline called floor acquisition ...multiple access (FAMA), which consists of both carrier sensing and a collision-avoidance dialogue between a source and the intended receiver of a packet. Control of the channel (the floor) is assigned to at most one station in the network at any given time, and this station is guaranteed to be able to transmit one or more data packets to different destinations with no collision with transmissions from other stations. The minimum length needed in control packets to acquire the floor is specified as a function of the channel propagation time. The medium access collision avoidance (MACA) protocol proposed by Karn and variants of CSMA based on collision avoidance are shown to be variants of FAMA protocols when control packets last long enough compared to the channel propagation delay. The throughput of FAMA protocols is analyzed and compared with the throughput of non-persistent CSMA. This analysis shows that using carrier sensing as an integral part of the floor acquisition strategy provides the benefits of MACA in the presence of hidden terminals, and can provide a throughput comparable to, or better than, that of non-persistent CSMA when no hidden terminals exist.
Over the past 20 years, there have been amazing strides toward integration of employees with disabilities internationally. The progress and barriers to such integration are described from an ...international perspective. Even though different nations have achieved differing levels of sophistication, the goals, processes, and barriers to full engagement are consistent around the world.
Investigated the employment outcomes of 103,417 rehabilitants, representing 13 disability categories. For each disabling condition, the top five occupations were reported. Results indicate that there ...was great similarity across the disability categories in types of employment, emphasizing the greater influence of functional abilities as opposed to disability category in job placement. (RJM)
Case narratives of 104 clients were scored and interpreted to determine the proportions of employment-rehabilitation target words in context that indicated without client involvement or with client ...involvement. Content analysis of 15,436 sentences indicated that percentages for rehabilitants and post-plan participants were higher then for plan-only participants. Clients with competitive work histories had greater percentages of involvement. (Author/MKA)
Examines the employment outcomes of 100,375 rehabilitants. Emphasizes the relationships among (1) full-time workers and those completing a rehabilitation plan and job openings in the United States, ...(2) starting salaries of full-time workers in the U.S. compared to rehabilitants, and (3) rehabilitation placements in occupations with the largest numerical increases. (RJM)
A family of medium access control protocols for single-channel packet radio networks is specified and analyzed. These protocols are based on a new channel access discipline called floor acquisition ...multiple access (FAMA), which consists of both carrier sensing and a collision-avoidance dialogue between a source and the intended receiver of a packet. Control of the channel (the floor) is assigned to at most one station in the network at any given time, and this station is guaranteed to be able to transmit one or more data packets to different destinations with no collision with transmissions from other stations. The minimum length needed in control packets to acquire the floor is specified as a function of the channel propagation time. The medium access collision avoidance (MACA) protocol proposed by Karn and variants of CSMA based on collision avoidance are shown to be variants of FAMA protocols when control packets last long enough compared to the channel propagation delay. The throughput of FAMA protocols is analyzed and compared with the throughput of non-persistent CSMA. This analysis shows that using carrier sensing as an integral part of the floor acquisition strategy provides the benefits of MACA in the presence of hidden terminals, and can provide a throughput comparable to, or better than, that of non-persistent CSMA when no hidden terminals exist.
