Perceptual automaticity in expert chess players: parallel encoding of chess relations.

A check detection task in a 5 x 5 section of the chessboard, containing a King and one or two potential checking pieces was employed. The checking status (i.e., the presence or absence of a check) and the number of attackers (one or two) were manipulated. It was found that the reaction time cost for adding a distractor was differentially greater in no trials than yes trials for novice, but not for expert, chess players. In addition, we contrasted standard check detection trials with trials in which one of two attackers was cued (colored red) and the task was to determine the checking status of the cued attacker while ignoring the other attacker. We documented a Stroop-like interference effect on trials in which a cued nonchecking attacker appeared together with an attacker that was checking (i.e., incongruent). These findings suggest automatic and parallel encoding procedures for chess relations in experts.

Visual span in expert chess players: evidence from eye movements.

The reported research extends classic findings that after briefly viewing structured, but not random, chess positions, chess masters reproduce these positions much more accurately than less-skilled players. Using a combination of the gaze-contingent window paradigm and the change blindness flicker paradigm, we documented dramatically larger visual spans for experts while processing structured, but not random, chess positions. In addition, in a check-detection task, a minimized 3 x 3 chessboard containing a King and potentially checking pieces was displayed. In this task, experts made fewer fixations per trial than less-skilled players, and had a greater proportion of fixations between individual pieces, rather than on pieces. Our results provide strong evidence for a perceptual encoding advantage for experts attributable to chess experience, rather than to a general perceptual or memory superiority.

The perceptual aspect of skilled performance in chess: evidence from eye movements.

Expert and intermediate chess players attempted to choose the best move in five chess positions while their eye movements were monitored. Experts were faster and more accurate than intermediates in choosing the best move. Experts made fewer fixations per trial and greater amplitude saccades than did intermediates, but there was no difference in fixation duration across skill groups. Examining the spatial distribution of the first five fixations for each position by skill group revealed that experts produced more fixations on empty squares than did intermediates. When fixating pieces, experts produced a greater proportion of fixations on relevant pieces than did intermediates. It is argued that expert chess players perceptually encode chess configurations, rather than individual pieces, and, consequently, parafoveal or peripheral processing guides their eye movements, producing a pattern of saccadic selectivity by piece saliency.

Low cytokine contamination in buffy coat-derived platelet concentrates without filtration.

BACKGROUND: Cytokines (interleukin [IL]-1 beta, IL-6, and tumor necrosis factor [TNF]) generated by white cells during the storage of platelet concentrates can cause febrile nonhemolytic transfusion reactions. The high rate of febrile reactions reported in other studies was not observed in the patients in the authors' center. This discrepancy prompted the determination of cytokine levels in buffy coat-derived platelet concentrates. STUDY DESIGN AND METHODS: Platelet concentrates were produced from buffy coats by a standard large-scale production process. Buffy coats were separated from the red cell and plasma components, and then platelets were recovered from the buffy coats by a soft-spin procedure. Levels of cytokines (IL-1 beta, IL-6, IL-8, and TNF) were determined with commercial enzyme-linked immunosorbent assays. RESULTS: In platelet concentrates produced by the buffy coat method, IL-1 beta, IL-6, IL-8, and TNF were observed at or below the detection limit of current enzyme-linked immunosorbent assays after 5 days' storage at 22 +/- 2 degrees C. Therefore, prestorage filtration had no measurable effect on cytokine levels. In controls, IL-1 beta, IL-6, IL-8, and TNF were quantitatively detected after exogenous addition of recombinant cytokines or exposure to lipopolysaccharide. CONCLUSION: Platelet concentrates prepared from buffy coats may be virtually free of cytokines (IL-1 beta, IL-6, IL-8, and TNF) during 5 days of storage. Filtration is not required to reduce the recipient's cytokine exposure via such platelet concentrates.

Preparation and heat-treatment of factor-IX-concentrates.

The stability to dry heat of different prothrombin complex concentrates depends on their composition, i.e. on the way of preparation and on additives such as reducing or non-reducing sugars. Alcohol precipitation, for instance, and addition of fructose or sorbitol as stabilizers is unsuitable for products which are intended to be heat-treated in the lyophylized state. Among the tests applied, only clotting-factor activities and--to a minor degree--turbidity, measured at 650 nm, responded significantly to small changes in heat-treatment. Finally, we were able in good yield to produce a factor IX high potency concentrate by adsorption on DEAE-Sephadex and ammonium sulphate precipitations. The freeze dried material can be heated for up to 96 hours and 70 degrees C without any sign of denaturation.

[Collection of thrombocyte concentrates and coagulation active fresh plasma with the Haemonetics PCS system]. / Gewinnung von Thrombozytenkonzentraten und gerinnungsaktivem Frischplasma mit dem System Haemonetics PCS.

More intensive chemotherapeutic regimens in patients with leukemia or malignant disease lead to an increasing demand for platelet concentrates. As conventional preparation of platelets from fresh whole blood is limited by the number of blood donors, new methods have to be investigated. Plasmapheresis with simultaneous collection of platelets is favored. We tested the new Haemonetics PCS system (Haemonetics Corp., Braintree, Mass.). Beside the effectivity of the measure, we were interested in the quality of the products. The simultaneous collection of hemostatic active plasma and platelet concentrates did not produce the same quality as our routine products.

In vitro effect on stored red blood cells and platelets after a 15-hour delayed refrigeration of whole blood prior to component preparation in CPD-AD.

We extended the time of keeping whole blood at 20-24 degrees C to 15 h (overnight) after phlebotomy for preparing platelet concentrates. We have evaluated the in vitro characteristics of platelets and blood cells prepared from whole blood drawn into CPD-AD, an anticoagulant containing 0.4 mM adenine and 1.5 times more dextrose than CPD. We studied in vitro red cell and platelet function of blood cooled either within 4 h after collection or after a 15-hour delay. In vitro platelet function measured as hypotonic shock reaction, aggregation response to ADP and collagen and 14C-serotonin uptake were not significantly different after preparation and after a 5-day storage period. Units held at room temperature for 15 h after blood collection exhibited a level of 2,3-DPG that was 45% of that exhibited by red cells held for 15 h at 1-6 degrees C. All other in vitro parameters of red cell concentrates measured during 35 days of storage were not significantly different. Based on these in vitro data blood drawn into CPD-AD might be kept up to 15 h at room temperature prior to refrigeration in order to prepare platelet concentrates.

[Stability of blood coagulation factors in deep frozen fresh plasma by storage at -20 degrees C and -40 degrees C]. / Die Stabilität von Faktoren des Gerinnungssystems im tiefgefrorenen Frischplasma während der Lagerung bei -20 grade C und -40 grade C.

Fresh frozen plasma (FFP), was shock-frozen to -25 degrees C within six hours after blood donation. The platelet count was reduced to 20 000/mm3. Aliquots were stored at -20 degrees C and -40 degrees C up to 24 months. Quick, PTT, factor V, VIII, IX, thrombin, antithrombin III, plasminogen, plasma-prekallikrein and kallikrein were determined monthly. With respect to the parameters investigated there was no significant difference between storage at -20 degrees C and -40 degrees C. Factor VIII loss was 10% after 12 months of storage. The activity of factor IX and V remained unchanged during 12 months, then factor V increased during storage. The other parameters did not change. Our study indicates quality of FFP seems not primarily depend on storage temperature, but an optimal preparation technique is much more important.

[Deep frozen fresh plasma in blood component therapy: preparation--quality control--indications]. / Das tiefgefrorene Frischplasma in der Blutkomponententherapie: Herstellung--Qualitätskontrolle--Indikation.

Fresh frozen plasma is prepared within 6 hrs after collection in a double bag system. A second centrifugation at 4600 x g is necessary to obtain a platelet poor plasma. A special bag freezing system fitted to a conventional cryostat and cooled with ethanol to -50 degrees C was developed to reach the required cooling rate. It is possible to freeze 25 plasma bags simultaneously within 30 min in this new apparatus. Fresh frozen plasma prepared in this manner contains all coagulation factors and inhibitors with almost normal activities. Freezing at -40 degrees C in the air, prolonged storage of the starting material, or insufficient cooling of the frozen product deteriorate its quality. The influence of these variables with the discussed in detail. Indications of fresh frozen plasma, especially for dilution- and posttraumatic consumption coagulopathy as well as liver disease, are presented.

[Microaggregates in stored blood: comparative evaluation of whole blood and buffycoat-free red cell concentrates (author's transl)]. / Mikroaggregate im gelagerten Blut. Vergleichende Untersuchungen an Vollblut und buffycoatfreiem Erythrocytenkonzentrat.

Routine preparation of red cell concentrates in our institute removes 90% of platelets and 70% of leucocytes in whole blood. Microaggregate formation in whole blood and red cell concentrates was comparatively evaluated by blood passage through a membrane filter with a pore size of 12 micron. Dry weight residues on the filter due to microaggregates were 5 to 10 times lower in red cell concentrates as compared to whole blood at any point of a 20 day storage period. In addition, the decrease in flow rate with increasing storage time was much more marked for whole blood than for red cell concentrates.

[Technical problems in platelet-concentrate preparation and their clinical significance]. / Technische Probleme der Thrombozytenkonzentratherstellung und ihre klinische Bedeutung.

To obtain platelet concentrates the following procedure is in routine use in the German Red Cross Blood Bank in Ulm: 1. Harvesting of donor blood in a double bag system; 2. two step centrifugation of a) whole blood, and b) platelet rich plasma at room temperature (22 degrees C) at 300 X g for 20 min, and 1200 X g for 30 min respectively; 3, resuspension of platelets in a minimum of 50 ml of plasma. Platelet yield averages 60%. The white cell content is less than 5% as compared to the original material. Although red cells are nearly absent the ABO blood group system and the D antigen are considered for compatibility. Platelet concentrates are stores up to 72 hours at 22 degrees C at constant slow rotation. Technical and biological variables affecting platelet yield and viability are discussed in some detail.

[Erythrocyte concentrate instead of whole blood: perspectives for blood banks and clinical therapy]. / Erythrozytenkonzentrat anstatt Vollblut: Perspektiven für Blutbank und Klinik

In 1974 some 117 000 units of blood were collected by the German Red Cross Blood Center in Ulm. Some 65 000 units were distributed to hospitals, mainly as whole blood. The surplus blood units (44%) were used for the preparation of plasma products. On 1 October 1974 glass bottles were replaced by plastic blood bags. The same date was chosen for the introduction of buffycoatfree red cell concentrates. It proved possible to replace whole blood almost entirely (92% of all blood units) by red cell concentrates within a few days after the deadline. The factors which prompted the clinicians to follow this new policy are described, and the clinical and economic implications are discussed.