Good vibrations: tactile feedback in support of attention allocation and human-automation coordination in event-driven domains

Observed breakdowns in human-machine communication can be explained, in part, by the nature of current automation feedback, which relies heavily on focal visual attention. Such feedback is not well suited for capturing attention in case of unexpected changes and events or for supporting the parallel processing of large amounts of data in complex domains. As suggested by multiple-resource theory, one possible solution to this problem is to distribute information across various sensory modalities. A simulator study was conducted to compare the effectiveness of visual, tactile, and redundant visual and tactile cues for indicating unexpected changes in the status of an automated cockpit system. Both tactile conditions resulted in higher detection rates for, and faster response times to, uncommanded mode transitions. Tactile feedback did not interfere with, nor was its effectiveness affected by, the performance of concurrent visual tasks. The observed improvement in task-sharing performance indicates that the introduction of tactile feedback is a promising avenue toward better supporting human-machine communication in event-driven, information-rich domains.     

An investigation of liquid carryover and sample residual for a high-throughput flow cytometer sample delivery system

The phenomenon of intersample contamination in air-segmented continuous-flow assays has been studied for many years, and new uses are being found for these sampling techniques every day. One application that has been developed recently employs a flow cytometer to conduct high-throughput screening assays of biological compounds. We have explored the sources of intersample contamination in the system and shown how methods developed previously can be applied to describe these phenomena. Using a simple model, we were able to accurately measure liquid film thickness in the sample tubing and demonstrate the effects of intersample contamination in a flow cytometer assay. Also, measures have been taken to reduce the level of intersample contamination in cytometric screening assays, helping to make the system a more viable tool for drug screening applications.     

The advantages of a negative branch unstable resonator for use with free-electron lasers

The sensitivity to misalignment of an almost concentric stable resonator is compared to that of a negative branch confocal unstable resonator, with specific applications to free-electron lasers. The practicability of both resonators is examined for both grazing and normal incidence configurations within the constraints of maximum feasible length, finite angular stability of resonator mirrors, size (determined by cooling requirements) of laser beam on mirrors, and minimum electron beam spot size in the wiggler. For the examples presented, a numerical fast Fourier transform propagation code was used.     

Rayleigh fading channels in mobile digital communication systems.II. Mitigation

For pt. I see ibid., vol. 35, no. 7, p. 90, 1997. In Part I of this tutorial, the major elements that contribute to fading and their effects in a communication channel were characterized. In Part II, these phenomena are briefly summarized, and emphasis is then placed on methods to cope with these degradation effects. Two particular mitigation techniques are examined: the Viterbi equalizer implemented in the Global System for Mobile Communication (GSM), and the RAKE receiver used in CDMA systems built to meet Interim Standard 95 (IS-95)     

Effect of 28 days of creatine ingestion on muscle metabolism and performance of a simulated cycling road race

Purpose

The effects of creatine supplementation on muscle metabolism and exercise performance during a simulated endurance road race was investigated.

Methods

Twelve adult male (27.3 ± 1.0 yr, 178.6 ± 1.4 cm, 78.0 ± 2.5 kg, 8.9 ± 1.1 %fat) endurance-trained (53.3 ± 2.0 ml* kg^-1* min^-1, cycling ~160 km/wk) cyclists completed a simulated road race on a cycle ergometer (Lode), consisting of a two-hour cycling bout at 60% of peak aerobic capacity (VO_2peak) with three 10-second sprints performed at 110% VO_{2 peak} every 15 minutes. Cyclists completed the 2-hr cycling bout before and after dietary creatine monohydrate or placebo supplementation (3 g/day for 28 days). Muscle biopsies were taken at rest and five minutes before the end of the two-hour ride.

Results

There was a 24.5 ± 10.0% increase in resting muscle total creatine and 38.4 ± 23.9% increase in muscle creatine phosphate in the creatine group (P < 0.05). Plasma glucose, blood lactate, and respiratory exchange ratio during the 2-hour ride, as well as VO_{2 peak}, were not affected by creatine supplementation. Submaximal oxygen consumption near the end of the two-hour ride was decreased by approximately 10% by creatine supplementation (P < 0.05). Changes in plasma volume from pre- to post-supplementation were significantly greater in the creatine group (⁺14.0 ± 6.3%) than the placebo group (^-10.4 ± 4.4%; P < 0.05) at 90 minutes of exercise. The time of the final sprint to exhaustion at the end of the 2-hour cycling bout was not affected by creatine supplementation (creatine pre, 64.4 ± 13.5s; creatine post, 88.8 ± 24.6s; placebo pre, 69.0 ± 24.8s; placebo post 92.8 ± 31.2s: creatine vs. placebo not significant). Power output for the final sprint was increased by ~33% in both groups (creatine vs. placebo not significant).

Conclusions

It can be concluded that although creatine supplementation may increase resting muscle total creatine, muscle creatine phosphate, and plasma volume, and may lead to a reduction in oxygen consumption during submaximal exercise, creatine supplementation does not improve sprint performance at the end of endurance cycling exercise.     

Evidence for a third component in neutrophil aggregation: potential roles of O-linked glycoproteins as L-selectin counter-structures

The homotypic aggregation of neutrophils requires the participation of L-selectin and the beta 2-integrins, but it has not been clear whether the two receptors recognize one another as counter-structures or whether other adhesion molecules are involved. We have examined aggregation of live neutrophils with target populations, manipulated to alter expression of adhesive epitopes, using flow cytometry. A target population depleted of both L-selectin and activatable beta 2-integrin displayed an ability to aggregate with live neutrophils, suggesting that these two molecules are not counter-structures. We also found that an O-sialoglycoprotease (GCP) from Pasteurella haemolytica is capable of inhibiting homotypic aggregation. Neutrophils treated with GCP lose O-glycosylated proteins but retain L-selectin and activatable beta 2-integrin. One or more of the GCP substrates appears to function in L-selectin-dependent binding but not in beta 2-integrin-dependent binding. Together the data suggest a mechanism of aggregation that is analogous to leukocyte-endothelial cell adhesion in which a low-affinity carbohydrate-dependent interaction precedes a high-affinity integrin-dependent adhesion.     

Strategies for positioning fluorescent probes and crosslinkers on formyl peptide ligands

Chemoattractant receptors represent a major subset of the G-protein coupled receptor (GPCR) family. One of the best characterized, the N-formyl peptide receptor (FPR), participates in host defense responses of neutrophils. The features of the ligand which regulate its interaction with the FPR are well-known. By manipulating these features we have developed new ligands to probe structural and mechanistic aspects of the peptide-receptor interaction. Three ligand groups have been developed: 1) ligands containing a Lys residue located in positions 2 through 7 that can be conjugated to FITC (N-formyl-Met1-Lys2-Phe3-Phe4, N-formyl-Met1-Leu2-Lys3-Phe4, N-formyl-Met1-Leu2-Phe3-Lys4, N-formyl-Met1-Leu2-Phe3-Phe4-Lys5, N-formyl-nLeu1-Leu2-Phe3-nLeu4-Tyr5-Lys6 and N-formyl-Met1-Leu2-Phe3-Phe4-Gly5-Gly6-Lys7; 2) fluorescent pentapeptide ligands (N-formyl-Met-X-Phe-Phe-Lys(FITC) where X = Leu, Ala, Val or Gly); and 3) small crosslinking ligands where the photoaffinity crosslinker 4-azidosalicylic acid (ASA) was conjugated to Lys in positions 3 and 4 and p-benzoyl-phenylalanine (Bpa) was located in position 2 in N-formyl-Met1-Bpa2-Phe3-Tyr4. The peptides were characterized according to activity and affinity in human neutrophils and cell lines transfected with FPR. All of the peptides were agonists, with parallel affinity and activity. In the first group, the peptide activity decreases as Lys is placed closer to the N-formyl group and the activity is improved by 1-3 orders of magnitude by conjugation with FITC. In the second group, the dissociation rate of the peptide from the receptor increases as position 2 is replaced by aliphatic amino acids with smaller alkyl groups. In the third group, crosslinking ligands remain biologically active, display nM affinity and covalently label the FPR.     

New flow cytometric capabilities at the national flow cytometryresource

The authors provide a brief review of flow cytometry and a broad view of new flow cytometry technologies. A brief introduction to flow cytometry and cell sorting is provided along with a summary of current commercial capabilities. New developments designed to overcome current limitations are described in terms of capabilities and a characterization of their performance. New capabilities include Fourier transform flow cytometry, phase sensitive detection, digital data acquisition, data clustering algorithms, high speed sorting, and slit scanning     

Transformation of mycosis fungoides: T-cell receptor beta gene analysis demonstrates a common clonal origin for plaque-type mycosis fungoides and CD30+ large-cell lymphoma

We investigated the consequences of Sr2+ binding to the transport sites of sarcoplasmic reticulum (SR) Ca(2+)-ATPase for two fluorescent conformational probes located in different regions of the ATPase. Using SR vesicles in which Lys-515 in the ATPase had been previously labeled with fluorescein 5'-isothiocyanate (FITC), we found that the Sr(2+)-induced a drop in the fluorescein fluorescence of this FITC-labeled ATPase shifted toward lower Sr2+ concentrations than the Sr(2+)-induced rise in Trp fluorescence for the same FITC-labeled ATPase. The curve describing the Sr(2+)-dependent rise in Trp fluorescence had a characteristic asymmetric shape, and the changes in Trp fluorescence occurred in parallel with the activation by Sr2+ of pNPP hydrolysis by the ATPase. Analysis of these results in terms of the simplest scheme describing the sequential binding of the two Sr2+ ions suggests that under the conditions of these experiments, i.e. at neutral pH in the presence of potassium, the Sr(2+)-induced rise in the Trp fluorescence mainly reflected the formation of ATPase with two ions bound to the transport sites, whereas the binding of a single Sr2+ ion was virtually sufficient to reduce the fluorescence of bound FITC to its minimal level.