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At least 1,315 records · Page 73Linked to original sources
PubMed2004

Pharmacokinetics of controlled-release polymers in the subarachnoid space after subarachnoid hemorrhage in rabbits.

OBJECT: Implantation of controlled-release polymers into the subarachnoid space to deliver drugs for treatment of vasospasm after subarachnoid hemorrhage (SAH) is currently of interest. Among the issues regarding local delivery of drugs in the subarachnoid space, however, are the extent of diffusion and the rate of release of the loaded agents. In this study Evans blue dye (EBD) was loaded into controlled-release polymers and its pharmacokinetic properties were determined in vitro and in vivo by using a rabbit model of SAH. METHODS: Ethylene-vinyl acetate copolymer (EVAc) was loaded 40% (w:w) with EBD and its pharmacokinetics were spectrophotometrically determined in vitro by examining three EBD-EVAc polymers. Additional polymers were implanted either into the frontal lobe or into the cisterna magna of 16 New Zealand White rabbits. Subarachnoid hemorrhage was induced in eight of the animals by an injection of 1.5 ml of arterial blood into the cisterna magna. The animals were killed 3 or 14 days postoperatively, their brains and spinal cords were harvested, and samples of each were placed in formamide for dye extraction and quantification. Specimens were examined macroscopically and the concentrations of EBD were determined with the aid of a spectrophotometer. The EBD-EVAc polymers continuously released EBD over a 133-day period. The controlled release of the dye into the subarachnoid space in either location resulted in staining of the entire central nervous system (CNS) in rabbits when the polymers were placed either on the frontal lobe or in the cisterna magna. The EBD diffusion covered a distance of at least 40 cm. The presence of blood in the subarachnoid space did not interfere with the diffusion. CONCLUSIONS: In this study the authors define the rate and extent of diffusion of EBD from controlled-release polymers placed in the subarachnoid space under conditions of SAH. Evans blue dye diffused through the entire rabbit CNS, covering a distance greater than that of the longest dimension of the hemicircumference of the subarachnoid space around the human brain. The pharmacokinetic properties of EBD-EVAc polymers are comparable to those of antivasospasm agents that are successfully used in animal models of SAH.

Animals↗
PubMed2002

The spacing effect in the free recall of homogeneous lists: present and accounted for.

Memory performance nearly always improves as a function of the spacing between repetitions. However, previous studies indicated that college students exhibited no spacing effect in the free recall of lists composed exclusively of words sampled from a single semantic category. We explored this puzzling phenomenon in two experiments. We found that the spacing effect in free recall can occur with homogeneous lists. Most interestingly, the effect seems to depend on the number of items (lag) separating spaced repetitions. Short lags between spaced repetitions yield a spacing effect, whereas longer lags do not.

Cues↗
PubMed1991

The spacing effect in young children's free recall: support for automatic-process explanations.

The effect of spacing repetitions on children's free recall was investigated in two experiments. In Experiment 1, both 4-year-old children and 7-year-old children exhibited a spacing effect in free recall, and the magnitude of the effect did not change with age. In Experiment 2, free recall was examined as a function of spacing, age (3 years old vs. 4 years old) and presentation rate (1 vs. 2 vs. 5 sec per stimulus). A spacing effect was obtained that did not differ as a function of age or presentation rate. Of particular interest was the fact that 3-year-olds exhibited a strong spacing effect even when stimuli were presented at a very rapid 1-sec rate. The results support the hypothesis that fundamental memory mechanisms that operate relatively automatically are sufficient to produce a spacing effect in free recall.

Child↗
PubMed2001

Parallel effects of aging and time pressure on memory for source: evidence from the spacing effect.

Two experiments address the degree to which item memory-the ability to remember that a word has been presented-is dissociable from source memory, or the ability to remember the context of that word's presentation. Spacing (as opposed to massing) an item's two presentations leads young adults to endorse that item more often when they are instructed to recognize it and to reject it more often when they are instructed to exclude it. Old adults also enjoy beneficial effects of spacing when the item is to be recognized, but suffer detrimental effects of the spacing manipulation when the item is to be rejected: They falsely endorse the spaced to-be-rejected items more than the massed ones. This dissociation also obtains with young subjects under conditions of increased time pressure: Under normal decision conditions, the ability to endorse to-be-recognized items and to reject to-be-rejected items increases with spacing; under speeded conditions, the ability to reject the latter items decreases with spacing. The results support the notion that source memory is selectively impaired in the elderly and that it is difficult to access mnemonic information about source under time pressure.

Adult↗
PubMed2003

Computerizing reading training: evaluation of a latent semantic analysis space for science text.

The effectiveness of a domain-specific latent semantic analysis (LSA) in assessing reading strategies was examined. Students were given self-explanation reading training (SERT) and asked to think aloud after each sentence in a science text. Novice and expert human raters and two LSA spaces (general reading, science) rated the similarity of each think-aloud protocol to benchmarks representing three different reading strategies (minimal, local, and global). The science LSA space correlated highly with human judgments, and more highly than did the general reading space. Also, cosines from the science LSA spaces can distinguish between different levels of semantic similarity, but may have trouble in distinguishing local processing protocols. Thus, a domain-specific LSA space is advantageous regardless of the size of the space. The results are discussed in the context of applying the science LSA to a computer-based version of SERT that gives online feedback based on LSA cosines.

Artificial Intelligence↗
PubMed1999

Color spaces of color-normal and color-abnormal observers reconstructed from response times and dissimilarity ratings.

With multidimensional scaling analysis, color spaces were reconstructed from reaction times (RTs) required to make same-different judgements of pairs of 15 equiluminant colors and from dissimilarity ratings between them. In addition to normal trichromats, observers with red-green color deficiency were tested. Two main purposes were served by this study: (1) to compare spatial representations of colors derived from discriminative RTs with those derived from dissimilarity measures and (2) to examine whether the task may selectively affect the dimension reflecting, in color-abnormal spaces, the deficient red-green mechanism. Contradicting our hypothesis of lower dimensionality of RT spaces, as compared with rating spaces, no consistent differences in solution dimensionality were found. However, configurations derived from the two measures diverged. The rating procedure yielded the most logical results for recovering color space. The RT configuration revealed contraction in the tritanopic direction, indicating longer color processing when the short-wavelength mechanism is involved, and in addition, for color-abnormal observers, clustering in the protanopic and deuteranopic directions, indicating even longer processing by the deficient red-green mechanism. This finding implies that RTs are suitable for detecting temporal differences in color processing but, for that very same reason, rather ill-suited for reconstructing color spaces.

Adult↗
PubMed1978

Space allocation decisions in schools of allied health.

Growth is continuing in schools of allied health in terms of faculty, enrollments, the use of university-based clinics and in the volume of training facilities required for allied health education. At the same time, budgets for future expansion of facilities are likely to become more stringent. Thus, the efficient allocation of physical space within schools of allied health is extremely important and it will become more important in future years. This paper examines procedures for evaluating space needs in allied health schools. A number of possible approaches, and their strengths and weaknesses, are explored. Influences of the physical environment--of which space is a primary component--on behavior is considered in the context of allied health education and their implications for space allocation are explored. The likely effects of Occupational Safety and Health Administration (OSHA) regulations on space utilization are also examined. Throughout the analysis recommendations are made for the safe and effective use of the available physical space within which allied health education occurs.

Facility Design and Construction↗
PubMedDate not supplied

Will this open space work?

Northern Oil is moving offices, and CEO Fritz Schumacher wants to make the most of the move in this fictional case study. He believes that adopting an open-plan work space will reinvent how the company works, not to mention cut costs. Facilities manager Sasha Pasternak also supports the open plan. Her job would be easier, and her budget would stretch further, if Northern had standardized workstations and used partitions, not walls. And she likes the way the new design flattens the organization: everyone has the same amount of space and the same ergonomically sound furniture. The new building would have more conference rooms and just-in-time work spaces for employees who worked mostly off-site. And although she knew that initial meetings between the architects and Northern employees hadn't yielded much support for open space--people were attached to their private offices--she expected that people would warm to the idea. But when the new design was unveiled, employees were less than enthusiastic. They hurled questions like, How will workers concentrate if they can't shut their office doors? How will people have confidential meetings with their boss? And why would people stay at Northern when the competition offers them private offices? There was even talk of circulating a petition refusing to move to the new space. A week later, the architect presented revised plans to the project group. The new options would add costs and reduce the amount of space savings, but offering a choice to employees might make them feel less threatened. What should the project team do? Five commentators offer advice.

Administrative Personnel↗
PubMed2001

Conformation spaces of proteins.

We report a simple method for measuring the accessible conformational space explored by an ensemble of protein structures. The method is useful for diverse ensembles derived from molecular dynamics trajectories, molecular modeling, and molecular structure determinations. It can be used to examine a wide range of time scales. The central tactic we use, which has been previously employed, is to replace the true mechanical degrees of freedom of a molecular system with the conformationally effective degrees of freedom as measured by the root-mean squared cartesian distances among all pairs of conformations. Each protein conformation is treated as a point in a high dimensional euclidean space. In this article, we model this space in a novel way by representing it as an N-dimensional hypercube, describable with only two parameters: the number of dimensions and the edge length. To validate this approach, we provide a number of elementary test cases and then use the N-cube method for measuring the size and shape of conformational space covered by molecular dynamics trajectories spanning 10 orders of magnitude in time. These calculations were performed on a small protein, the villin headpiece subdomain, exploring both the native state and the misfolded/folding regime. Distinct features include single, vibrationally averaged, substate minima on the 0.1-1-ps time scale, thermally averaged conformational states that persist for 1-100 ps and transitions between these local minima on nanosecond time scales. Large-scale refolding modes appear to become uncorrelated on the microsecond time scale. Associated length scales for these events are 0.2 A for the vibrational minima; 0.5 A for the conformational minima; and 1-2 A for the nanosecond events. We find that the conformational space that is dynamically accessible during folding of villin has enough volume for approximately 10(9) minima of the variety that persist for picoseconds. Molecular dynamics trajectories of the native protein and experimentally derived solution ensembles suggest the native state to be composed of approximately 10(2) of these thermally accessible minima. Thus, based on random exploration of accessible folding space alone, protein folding for a small protein is predicted to be a milliseconds time scale event. This time can be compared with the experimental folding time for villin of 10-100 micros. One possible explanation for the 10-100-fold discrepancy is that the slope of the "folding funnel" increases the rate 1-2 orders of magnitude above random exploration of substates.

Algorithms↗
PubMed2001

Future space. A new blueprint for business architecture.

Although the Internet is an essential conduit for many business activities, it isn't rendering the physical world any less important, as the failures of many Web merchants demonstrate. People need social and sensual contact. The companies that succeed will be those best able to integrate the physical and the virtual. But that requires a new kind of business architecture--a new approach to designing stores, offices, factories, and other spaces where business is conducted. The author, a faculty member at Harvard Graduate School of Design, provides practical guidelines to help managers and entrepreneurs think creatively about the structures in which their businesses operate. He outlines four challenges facing designers of such "convergent" structures, so-called because they function in both physical and virtual space: matching form to function, allowing visitors to visualize the presence of others, personalizing spaces, and choreographing connectivity. Using numerous examples, from a fashion retailer that wants to sell in stores as well as through a Web site to a radically new kind of consulate, the author shows how businesses can meet each challenge. For instance, allowing customers to visualize the presence of others means that visitors to a Web site should be given a sense of other site visitors. Personalizing physical and virtual spaces involves using databases to enable those spaces to adapt quickly to user preferences. The success of companies attempting to merge on-line and traditional operations will depend on many factors. But without a well-designed convergent architecture, no company will fully reap the synergies of physical space and Internet technology.

Architecture↗
PubMedDate not supplied

Endoscopic transmaxillary biopsy of pterygopalatine space masses: a preliminary report.

INTRODUCTION: Although masses in the pterygomaxillary space are uncommon, they frequently present diagnostic challenges when they occur. If a tissue biopsy is required for pathological analysis, the relative inaccessibility of this region can make the surgical approach more extensive and technically difficult than seems justified. In this study, we describe a series of four cases in which a transnasal endoscopic technique was used to biopsy masses of the pterygomaxillary space. METHODS: The four patients described in this report had lesions of the pterygomaxillary space that were detected radiographically. The surgical approach involved an endoscopic uncinectomy and a wide maxillary antrostomy to provide maximum exposure of the posterior maxillary sinus wall. Careful opening of the bone and underlying periosteum provided ready access to the pterygomaxillary space in an atraumatic fashion. Biopsy specimens were talken under direct endoscopic visualization using traditional biopsy forceps. RESULTS: In each case, satisfactory exposure of the mass was achieved and diagnostic biopsy specimens were obtained. There were no adverse sequelae related to the procedure. One patient was returned to the operating room 2 weeks later for a repeat biopsy so that additional diagnostic studies could be performed. This was obtained easily through the previous antrostomy and posterior maxillary wall opening. CONCLUSIONS: The transnasal endoscopic approach to the pterygomaxillary space is a safe, relatively noninvasive technique that can be performed by otolaryngologists trained in endoscopic sinus surgery. This procedure allows adequate exposure of the pterygomaxillary space for biopsy while avoiding the morbidity of an open surgical approach.

Biopsy↗
PubMed2002

Space infection of the head and neck.

Deep neck infection may be lethal, especially when life-threatening complications occur. We conducted a retrospective analysis of 184 patients with deep neck infection who were treated at Kaohsiung Medical University Hospital during the past 6 years. Factors such as age, sex, hospitalization days, clinical presentations, involved spaces, imaging studies, microbiology, and treatment method were analyzed. There were 122 men and 62 women with a mean age of 41.7 years. The average hospitalization was 8.4 days. The involved spaces, determined by physical examination and radiologic findings, were the peritonsillar space (59 patients), parapharyngeal space (77 patients), submandibular space (55 patients), and retropharyngeal space (20 patients). Of the 49 patients for whom the origin of infection was identified, 29 were infected via the upper respiratory tract and 13 had infection of odontogenic origin. The most common isolated organism was Klebsiella pneumoniae. One hundred and thirty-seven patients (74.5%) underwent surgery, including repeated needle aspiration (87 patients) and surgical drainage (50 patients). The remaining 47 patients recovered uneventfully with antibiotic therapy alone. Eighteen patients developed life-threatening complications, such as descending mediastinitis, sepsis, airway obstruction, and jugular vein thrombosis. Two patients died of septic shock. The combination of accurate diagnosis, effective antibiotic therapy, airway maintenance, and intensive surgical debridement for those who fail to respond to conservative treatment will lead to a good prognosis.

Adolescent↗
PubMedDate not supplied

Continuous pump pressures cannot be used to identify catheter tip migration into the subarachnoid space.

BACKGROUND AND OBJECTIVES: Migration of an epidural catheter into the subarachnoid space is a potentially lethal complication of continuous epidural anesthesia. We evaluated the use of pump pressure measurement during infusion in detecting such an occurrence. METHODS: Pump pressures at two flow rates (P1 and P10) and epidural space pressure (P0) were measured hourly in eight consecutive ASA Physical Status I parturients receiving continuous epidural anesthesia and compared to those of a patient whose catheter migrated into the subarachnoid space. In addition, total resistance to infusion (Rtot) was calculated as the slope of the least squares regression line linking pressure and flow. Epidural resistance (Repi) was computed as the difference between total resistance and catheter resistance; Repi = Rtot - Rcath. RESULTS: In epidural catheters, average P0 and P10 were 13 +/- 4 mmHg and 23 +/- 4 mm Hg, respectively, and did not change over time. Rtot and Repi averaged 960 +/- 180 RU and 980 +/- 120 RU, respectively. Pump pressures in the subarachnoid catheter were 10 mmHg for P0 and 20 mmHg for P10, while Rtot was 1000 RU. CONCLUSIONS: We conclude that epidural and subarachnoid space resistance is essentially zero and the pump pressure in the system is used to overcome the catheter resistance. Both spaces offer the same total resistance to infusion and, therefore, pump pressure will not change when a catheter migrates into the subarachnoid space.

Anesthesia, Epidural↗
PubMed2003

[Osteoporosis and genes in space environment].

Based on observations of extreme and accelerated loss of bone density in astronauts flying on longer space missions, scientists coordinated by the European Space Agency, ESA, have since the mid 1990'ies been focusing on potential causes for this alarming finding. The experimental conditions on board space craft are however very restrictive, for which reason research into human physiology in the space environment has gone its own ways regarding how to create solid and statistically significant data. Space observations can profit markedly from ground-based simulations studies, and some interesting data on countermeasures against loss of bone matter, that have been tested in the recently completed 90-days bed rest study, are reported here. Paired with information on different phenotypes observed in such studies, the data reported looks very promising. This bed rest study has generated a set of extremely interesting data, which in terms of resolution and quality allows the researchers to consider this study as a significant step ahead, and as a crucial steppingstone in defining the next round of space based studies of bone metabolism. In addition the findings in the bed rest study are directly applicable to long-term bed ridden patients in terms of the need to maintain activity as a means to improve the recovery prognosis.

Adaptation, Physiological↗
PubMedDate not supplied

Space analysis: putting it all together.

Space analysis is the foundation of all orthodontic treatment plans and is critical in deciding whether functional and cosmetic orthodontic goals can be achieved. An organized, comprehensive, integrated space analysis will help dentists to choose between a variety of treatment approaches and to determine if permanent teeth must be extracted. At present, most of the literature focuses on individual aspects of space analysis; a search of the literature revealed only three published articles that involved integrating treatment planning with comprehensive space analysis. The mandibular arch is the template for this space analysis because it is less malleable than the maxilla. Using four key arch measurements as variables with a curve of Spee correction creates custom starting and final arch forms for each patient. This three-dimensional total arch form approach is incorporated into a spreadsheet template that integrates the individual aspects of space analysis into one unified approach while performing most of the calculations. The spreadsheet is available for free download at www.agd.org or www.herseycentral.org/drsolomon.

Cephalometry↗
PubMed2004

[Visualization of the parapharyngeal space of the Chinese visible human].

OBJECTIVE: To build digitized visible model of the parapharyngeal space(PPS) of Chinese visible human. METHOD: Cross-sectional images from the Chinese visible human data set were reviewed and the structures of the parapharyngeal space were confirmed on a section-by-section basis. Three-dimensional computer reconstructions of the parapharyngeal space and surrounding structures were generated from these data using PC and imaging software. RESULT: The three-dimensional reconstructed images displayed perfectly the anatomical relationships of the parapharyngeal space, parotid, muscles, mandible and vessels. All reconstructed structures can be represented individually or jointly, any diameter and angle of the structures reconstructed could be measured conveniently. CONCLUSION: The Chinese visible human data set can provide complete and accurate data. The digitized model of the parapharyngeal space and its surroundings offer unique insights into the complex anatomy, and provide morphological data for image diagnosis and operation of the parapharyngeal space.

Adipose Tissue↗
PubMed2004

[Serial thin cross-sectional anatomy and computerized three-dimensional reconstruction of metacarpal fascial spaces of hand].

OBJECTIVE: To build three-dimensional (3-D) visible model for surgical treatment of infection of fascial spaces of hand. METHODS: Serial thin cross-sections (0.2 mm) of hand were made by cryomicrotome, and the thin cross-sections of metacarpal parts were observed. A personal computer was employed to reconstruct 3-D model of metacarpal fascial space. RESULTS: The shapes, locations and adjacent relations of the mid-palmar space, thenar space and metacarpal bones were displayed clearly from computerized 3-D model, which could be the cross-reference of the cross-sections expediently. CONCLUSION: The computerized 3-D reconstruction of metacarpal fascial spaces can provide some guidance for surgical treatment of infection and other diseases of metacarpal fascial spaces.

Anatomy, Cross-Sectional↗
PubMed2004

[The study on color space of the VINTAGE & UNIBOND standard color].

OBJECTIVE: To research the color space of the standard color board, guide the clinic work of color match, and establish an foundation for deeper researching. METHODS: Through taking analysis of reflecting spectrum and spectral tristimulus, each parameter of the color on standard board was found out. The color difference between border upon colors on board was worked out through matching the color parameters. The number of color space between each border upon color on standard color board, divided by deltaE = 1.5, was found. RESULTS: The number of color space between each border upon color was 3-6. The color space was bigger in group B, but smaller in group D. The color space was bigger in high lightness area, but smaller in low lightness area. CONCLUSION: Some color space has been found between standard color borders of VINTAGE and UNIBOND. Color of natural teeth is unable to be completely included into standard color border, especially in clinical care.

Colorimetry↗