bluuebunny/crossref_metadata_2025 huggingface dataset:
Responding to Technological Change
Authors: Haynes Philip , Ip Ken , Saintas Patrick , Stanier Stan , Palmer Helen , Thomas Nicola , Reast Gareth , Barlow Joyce , Maillardet Fred
Published: June 2004

Six academics in a new university were seconded to the role of part-time learning technology support. It was necessary to have an informed view of the IT skills level of all academic teaching staff. A selfassessment questionnaire was designed based on the core competencies in the European Computer Driving Licence (ECDL). The results were used to offer a targeted pilot of a new online learning training method. Results showed considerable diversity in the range of IT skills. Over half (55%) of the staff could not use a range of IT software at a prescribed benchmark level. Staff were more likely to be skilled at word-processing and Internet tasks (average score above the benchmark) and less likely to be competent with presentations, spreadsheets and databases (average score below the benchmark). Staff working in science-based subjects tended to score higher. As a result of the survey, some staff were offered an online basic skills training programme. Staff liked the flexibility of this, but also found that they needed personal support and encouragement. It is necessary to raise the profile of IT skills and to argue for their relevance. A range of training opportunities is needed that will assist the needs and motivations of staff. Staff prefer training that they see as relevant to their subject area and professional context. Online software skills training does not provide a single solution, but can add an additional method that will appeal to some learners.
Persistence and the Adult Learner
Authors: Castles Jane
Published: June 2004

This research is part of a larger study of the factors affecting part-time adult learners. It covers a literature review dealing with three areas of factors that might affect adult learners: (i) social and environmental, (ii) traumatic and (iii) intrinsic factors. This produced 36 factors and was followed by a qualitative study to validate and refine the factors. This part of the research was undertaken with students from the Open University of the UK. The research resulted in the construction of a model of persistence containing 12 factors. The model was subjected to quantitative testing by questionnaire, and preliminary analysis showed that most of the factors were valid indicators of persistence. The model needs to be further refined in order to be predictive, but still indicates that institutions can help to overcome at least some of the problems preventing persistence.
Missing Data in Disguise and Implications for Survey Data Analysis
Authors: Wang Lin , Fan Xitao
Published: June 2004

The phenomenon was observed that more “not applicable” (NA) responses occurred for the items near the end of a survey instrument than for those at the beginning. In this article, the authors present evidence that this phenomenon represents missing data in disguise in a survey study, especially when the survey is long. They explore the implications for survey data analysis in this situation. Practical recommendations are made for survey instrument construction and survey data analysis to minimize the potential adverse effect of such missing data in disguise. Limitations of the study are also discussed.
Studying Culture as an Integral Aggregate Variable: Organizational Culture and Innovation in a Group of Nonprofit Organizations
Authors: Jaskyte Kristina , Dressler William W.
Published: June 2004

The appropriate level of analysis for the study of culture has been contested. There is a tradition of conceptualizing culture apart from the individuals who interact within a society. Alternately, there is a tradition of seeing culture only in the minds of individuals in society. The authors’ contention is that there is no choice here; both perspectives are valid and can be integrated within a single framework. Borrowing the concept of integral aggregate variable from epidemiology, they argue that there are both integral aggregate properties of culture and integral individual properties of culture. Both dimensions of culture can be examined using cultural consensus analysis. With data on organizational culture, the authors show how an investigator can move from one level of analysis to another. These results illustrate how integral aggregate properties of culture can be extracted from individual data using consensus analysis and be used as measures of aggregate units of analysis.
Reliability in Coding Open-Ended Data: Lessons Learned from HIV Behavioral Research
Authors: Hruschka Daniel J. , Schwartz Deborah , St.John Daphne Cobb , Picone-Decaro Erin , Jenkins Richard A. , Carey James W.
Published: June 2004

Analysis of text from open-ended interviews has become an important research tool in numerous fields, including business, education, and health research. Coding is an essential part of such analysis, but questions of quality control in the coding process have generally received little attention. This article examines the text coding process applied to three HIV-related studies conducted with the Centers for Disease Control and Prevention considering populations in the United States and Zimbabwe. Based on experience coding data from these studies, we conclude that (1) a team of coders will initially produce very different codings, but (2) it is possible, through a process of codebook revision and recoding, to establish strong levels of intercoder reliability (e.g., most codes with kappa 0.8). Furthermore, steps can be taken to improve initially poor intercoder reliability and to reduce the number of iterations required to generate stronger intercoder reliability.
Reflections on the NCSL from a Historical Perspective
Authors: Bolam Ray
Published: June 2004

This article reviews three historical phases of leadership development in England and Wales, together with parallel changes in in-service training and the broader professional infrastructure, in order to show how the idea of a national college developed and became viable. It argues that, as a policy innovation, the NCSL has built on earlier practice but also has several innovative features, including networked learning communities and its use of IT. It suggests that the transformational perspective should be interpreted in the framework of situational or pluralist theories of leadership. Finally, it considers some strategic issues affecting the college’s longer-term sustainability.
The International Role of the NCSL
Authors: Walker Allan , Dimmock Clive
Published: June 2004

This article addresses the international positioning and role of the National College for School Leadership (NCSL). The article argues that the college stands as an initiator, exporter, importer and disseminator of leadership research and practice and that the role it adopts in regard to these will determine its international influence. The first part of the article discusses the uniqueness of the college and the possible pathways along which its influence could expand. It acknowledges that in building its sphere of influence the college faces a context of unpredictability and uncertainty. The second part of the article focuses specifically on the international role of the NCSL and suggests that from among a range of alternatives, the college would be wise to adopt a confrere role, that is, genuinely mutual dialogue and co-operative learning relationship with researchers and partners overseas. The third part of the article recognizes the associated difficulties and complexities of adopting such a confrere role. It goes on to suggest that the likely benefits of such an approach would not only create a rich international learning environment for policy-makers and school leaders alike, but would also benefit the growing number of multicultural schools and communities in the UK.
The National College for School Leadership
Authors: Crow Gary M.
Published: June 2004

The growing interest internationally in leadership development and how leaders contribute to student learning makes the development of the National College for School Leadership (NCSL) an intriguing and potentially significant event. This article examines the aims and programs of the NCSL from a North American perspective. Based on a context in which the world of leadership work is changing and the socialization of school leaders is critical, the article identifies opportunities and challenges which the NCSL faces in contributing to the reform of leadership and leadership development.
Organizational Life Cycles and the Development of the National College for School Leadership
Authors: Mulford Bill
Published: June 2004

This article employs organizational life cycle, organizational learning stages and group development stages literature to examine my experiences at the National College for School Leadership (NCSL) during its establishment phase. Support was found, and other foci suggested, for this literature. As well, future issues to be faced by the NCSL were suggested, such as domain expansion and further decentralization and developing the maturity to be able to accommodate those who wish to be constructively critical of its activities.
Making a Difference?
Authors: Earley Peter , Evans Jennifer
Published: June 2004

This article discusses of some of the methodological issues involved in attempting to ascertain or measure the impact of the National College for School Leadership on the leaders of English schools and leadership development more generally. It does so with specific reference to the findings of two surveys of heads and deputies of English state schools conducted in 2001 and 2003, the first commissioned by the (then) Department for Education and Employment, and the second by the NCSL. The findings of the two surveys, specifically those relating to: a) the adequacy of preparation for headship; and b) the role of the college, are compared and used to illustrate the value and limitations of baseline and follow-up studies as impact measures. Methodological approaches and research designs which could be developed to help ascertain more rigorously the impact of the college are also briefly considered.
A Response from the National College for School Leadership
Authors: Southworth Geoff
Published: June 2004

This article provides a response to the previous papers. It sets out a descriptive overview of the National College for School Leadership and then discusses issues of: scale; on-the-job learning; innovation as technological and networking; start-up organisations; leadership effects; international awareness; evaluating leadership and impact. The article closes with reflections on three things: (1) sensitivity to context; (2) capacity building; and (3) leadership and complexity theory.
A novel role for STAT1 in regulating murine erythropoiesis: deletion of STAT1 results in overall reduction of erythroid progenitors and alters their distribution
Authors: Halupa Adrienne , Bailey Monica L. , Huang Kai , Iscove Norman N. , Levy David E. , Barber Dwayne L.
Published: June 2004

Erythropoietin (EPO) activates many distinct signal transduction cascades on engagement of its receptor. Deletion of the EPO, EPO receptor (EPO-R), or JAK2 genes in mice results in embryonic lethality due to a fatal anemia. EPO activates signal transducer and activator of transcription 1 (STAT1), STAT3, and STAT5a/b transcription factors in erythroid cell lines. Studies have focused on STAT5 as the primary target of EPO-dependent JAK2 activation. However, STAT5a/b–/– mice are viable, displaying a nonfatal anemia during embryogenesis, and delayed differentiation in adult erythropoiesis. Importantly, EPO-R cytoplasmic tyrosines are dispensable for viability in vivo. Interestingly, no cytoplasmic tyrosines are required for phosphorylation of STAT1. This led us to examine whether STAT1-deficient mice have altered erythropoiesis. A shift in erythropoiesis was observed in STAT1–/– mice, with reduced bone marrow-derived erythroid colony-forming units (CFU-Es) and a compensatory increase in splenic burst-forming units (BFU-Es) and CFU-Es. Both types of splenic-derived cells displayed EPO hyperresponsiveness. A 1.6-fold reduction in total CFU-Es was observed in STAT1-deficient mice, whereas total BFU-Es were comparable. Flow cytometry of STAT1-deficient erythroid cells revealed a less differentiated phenotype, associated with increased apoptosis of early erythroblasts. STAT1-deficient erythroblasts from phenylhydrazine-primed mice displayed enhanced phosphorylation of STAT5a/b, Erk1/2, and protein kinase B (PKB)/Akt. These results illustrate that STAT1 plays an important role in the regulation of erythropoiesis.
Activated polymorphonuclear neutrophils disseminate anti-inflammatory microparticles by ectocytosis
Authors: Gasser Olivier , Schifferli Jürg A.
Published: June 2004

On activation, human neutrophils release microparticles, called ectosomes, directly from the cell surface membrane. Microparticles from platelets, endothelial cells, and monocytes were reported to support coagulation or to modulate vascular homeostasis by activating monocytes as well as endothelial cells. We find that neutrophil ectosomes have no proinflammatory activity on human macrophages as assessed by the release of interleukin 8 (IL-8) and tumor necrosis factor α (TNFα). On the contrary, ectosomes increase the release of transforming growth factor β1 (TGFβ1), suggesting that ectosomes down-modulate cellular activation in macrophages. Polymorphonuclear neutrophil (PMN) ectosomes are able to block inflammatory response of macrophages to zymosan and lipopolysaccharide (LPS). We show that an early-phase TGFβ1 secretion and the exposure of phosphatidylserine on the surface of ectosomes independently contribute to this effect. Ectosome-cell contact was sufficient for their immunomodulatory function as shown by blocking phagocytosis with cytochalasin D. Thus, neutrophils release potent anti-inflammatory effectors, in the form of ectosomes, at the earliest stage of inflammation, already providing a drive to its resolution.
IL-4 alone without the involvement of GM-CSF transforms human peripheral blood monocytes to a CD1adim, CD83+ myeloid dendritic cell subset
Authors: Roy Keshab Chandra , Bandyopadhyay Gautam , Rakshit Srabanti , Ray Mitali , Bandyopadhyay Santu
Published: June 2004

Myeloid dendritic cells (DCs) are conventionally generated by culturing human peripheral blood monocytes in the presence of GM-CSF and IL-4. Here we report that IL-4 alone, in the absence of detectable endogenous GM-CSF, transforms human peripheral blood monocytes to a CD1adim DC subset that could be matured to CD83+ DCs. Absence of endogenous GM-CSF in IL-4-DC was demonstrated by RT-PCR and flow cytometry. With the exception of CD1a expression, surface marker, morphology and phagocytic activity of these DCs (IL-4-DC) were similar to myeloid DCs (GM-IL-4-DC) conventionally generated in the presence of GM-CSF and IL-4. Conventional GM-IL-4-DC produced less IL-12 compared with IL-4-DC after stimulation with anti-CD40 monoclonal antibody, or LPS plus IFN-γ, although the difference was more prominent when LPS plus IFN-γ was used as the stimulus. The GM-IL-4-DC also induced less frequent IFN-γ+ T cells in a mixed leukocyte reaction (MLR) than that of IL-4-DC. Yields of IL-4-DCs were marginally lower than that of GM-IL-4-DCs. Our data indicate that peripheral blood monocytes can be transformed to CD1a-deficient myeloid DCs solely by IL-4, and these IL-4-DCs are likely to induce a stronger Th1 response than conventional GM-IL-4-DCs.
DNA damage checkpoint maintenance through sustained Chk1 activity
Authors: Latif Christine , Elzen Nicole R. den , O'Connell Matthew J.
Published: June 2004

The G2 DNA damage checkpoint prevents mitotic entry in the presence of DNA damage. This requires the activation of the phosphoinositide-3-kinase-related protein kinases ATR and ATM in human cells and the ATR homologue Rad3 in the fission yeast Schizosaccharomyces pombe. Rad3 activates the effector protein kinase Chk1 by phosphorylation. However, in fission yeast, inactivation of Rad3 following checkpoint activation has no impact on checkpoint duration. This demonstrates that Rad3 is not required for checkpoint maintenance and that the processes of checkpoint initiation and maintenance are distinct. Chk1 is required for checkpoint initiation but its role in checkpoint maintenance has not been investigated. We show here that Chk1 kinase activity is rapidly induced following irradiation and is maintained for the duration of a checkpoint arrest. On entry to mitosis, there is a transient decrease in Chk1 activity and phosphorylation, but Chk1 activity remains higher than that observed in unirradiated cells. We have generated temperature-sensitive alleles of chk1, which phenocopy chk1 deletion at the non-permissive temperature. Using these alleles, we have shown that inactivation of Chk1 during a checkpoint arrest leads to premature checkpoint termination, resulting in catastrophic mitoses that are a hallmark of checkpoint failure. Therefore, unlike Rad3, Chk1 is an important determinant of both checkpoint initiation and maintenance.
Azithromycin for Improving Pulmonary Function in Cystic Fibrosis
Authors: Carr Roxane R , Nahata Milap C
Published: June 2004

OBJECTIVE:

To review the literature concerning the use of azithromycin in the treatment of patients with cystic fibrosis (CF).

DATA SOURCES:

A search of MEDLINE (1966–April 2004), Embase (1980—April 2004), and International Pharmaceutical Abstracts (1971–April 2004) was performed. Search terms included cystic fibrosis, macrolide, and azithromycin.

DATA SYNTHESIS:

Four studies have been performed in 7–185 patients (children and adults) over a 3- to 6-month period. The azithromycin dosage ranged from 250 mg 3 times weekly to 500 mg daily. The trials reported an improvement in percent predicted forced expiratory volume ranging from 2.95% to 6.2% in patients treated with azithromycin compared with those receiving placebo.

CONCLUSIONS:

Azithromycin appeared to improve pulmonary function in adults and older children with CF and was well tolerated when administered for 6 months. Further research is needed to determine an optimal dosage regimen, duration of treatment, effects on quality of life, and cost-effectiveness of azithromycin therapy.
Reducing Clinically Significant Gastrointestinal Toxicity Associated with Nonsteroidal Antiinflammatory Drugs
Authors: Jacobsen Ryan B , Phillips Beth Bryles
Published: June 2004

OBJECTIVE:

To evaluate the efficacy of treatment strategies to reduce clinically significant gastrointestinal adverse effects associated with nonsteroidal antiinflammatory drugs (NSAIDs).

DATA SOURCES:

A MEDLINE search (1966–November 2003) was performed to identify relevant articles. Key search terms included proton-pump inhibitors, histamine H2 antagonists, misoprostol, cyclooxygenase-2 (COX-2) selective inhibitors, nonsteroidal antiinflammatory agents, stomach ulcer, prevention, and economics. Additional references were obtained from cross-referencing the bibliographies of selected articles.

STUDY SELECTION AND DATA EXTRACTION:

All information obtained from the MEDLINE search was reviewed. To provide the most clinically relevant information, only randomized controlled trials are included in this review.

DATA SYNTHESIS:

Clinically significant upper gastrointestinal adverse events, such as ulcers and ulcer complications, associated with NSAIDs are a cause of significant morbidity and mortality in the US. Interest in strategies to reduce the risk of these adverse events is high among clinicians and patients. Misoprostol, high-dose H2-receptor antagonists, proton-pump inhibitors, and COX-2 inhibitors have been shown to reduce this risk. Misoprostol and proton-pump inhibitors are more effective than H2-receptor antagonists; dose-related diarrhea limits the clinical utility of misoprostol. These strategies may not provide enough protection in patients taking concomitant low-dose aspirin therapy or patients with a history of ulcer complications.

CONCLUSIONS:

COX-2 inhibitors and proton-pump inhibitors are effective and well-tolerated therapies to reduce clinically significant upper gastrointestinal adverse events associated with NSAIDs.
A Retinal-Specific Regulator of G-Protein Signaling Interacts with Gαoand Accelerates an Expressed Metabotropic Glutamate Receptor 6 Cascade
Authors: Dhingra Anuradha , Faurobert Eva , Dascal Nathan , Sterling Peter , Vardi Noga
Published: June 2004

Gois the most abundant G-protein in the brain, but its regulators are essentially unknown. In retina, Gαo1is obligatory in mediating the metabotropic glutamate receptor 6 (mGluR6)-initiated ON response. To identify the interactors of Go, we conducted a yeast two-hybrid screen with constituitively active Gαoas a bait. The screen frequently identified a regulator of G-protein signaling (RGS), Ret-RGS1, the interaction of which we confirmed by coimmunoprecipitation with Gαoin transfected cells and in retina. Ret-RGS1 localized to the dendritic tips of ON bipolar neurons, along with mGluR6 and Gαo1. When Ret-RGS1 was coexpressed inXenopusoocytes with mGluR6, Gαo1, and a GIRK (G-protein-gated inwardly rectifying K+) channel, it accelerated the deactivation of the channel response to glutamate in a concentration-dependent manner. Because light onset suppresses glutamate release from photoreceptors onto the ON bipolar dendrites, Ret-RGS1 should accelerate the rising phase of the light response of the ON bipolar cell. This would tend to match its kinetics to that of the OFF bipolar that arises directly from ligand-gated channels.
Defective Neuronal Development in the Mushroom Bodies ofDrosophila Fragile X Mental Retardation 1Mutants
Authors: Michel Carlos I. , Kraft Robert , Restifo Linda L.
Published: June 2004

Fragile X mental retardation 1(Fmr1) is a highly conserved gene with major roles in CNS structure and function. Its product, the RNA-binding protein FMRP, is believed to regulate translation of specific transcripts at postsynaptic sites in an activity-dependent manner. Hence,Fmr1is central to the molecular mechanisms of synaptic plasticity required for normal neuronal maturation and cognitive ability. Mutations in itsDrosophilaortholog,dfmr1, produce phenotypes of brain interneurons and axon terminals at the neuromuscular junction, as well as behavioral defects of circadian rhythms and courtship. We hypothesized thatdfmr1mutations would disrupt morphology of the mushroom bodies (MBs), highly plastic brain regions essential for many forms of learning and memory. We found developmental defects of MB lobe morphogenesis, of which the most common is a failure of β lobes to stop at the brain midline. A similar recessive β-lobe midline-crossing phenotype has been previously reported in the memory mutantlinotte. Thedfmr1MB defects are highly sensitive to genetic background, which is reminiscent of mammalian fragile-X phenotypes. Mutations ofdfmr1also interact with one or more third-chromosome loci to promote α/β-lobe maturation. These data further support the use of theDrosophilamodel system for study of hereditary cognitive disorders of humans.
The GDP-GTP Exchange Factor Collybistin: An Essential Determinant of Neuronal Gephyrin Clustering
Authors: Harvey Kirsten , Duguid Ian C. , Alldred Melissa J. , Beatty Sarah E. , Ward Hamish , Keep Nicholas H. , Lingenfelter Sue E. , Pearce Brian R. , Lundgren Johan , Owen Michael J. , Smart Trevor G. , Lüscher Bernhard , Rees Mark I. , Harvey Robert J.
Published: June 2004

Glycine receptors (GlyRs) and specific subtypes of GABAAreceptors are clustered at synapses by the multidomain protein gephyrin, which in turn is translocated to the cell membrane by the GDP-GTP exchange factor collybistin. We report the characterization of several new variants of collybistin, which are created by alternative splicing of exons encoding an N-terminalsrchomology 3 (SH3) domain and three alternate C termini (CB1, CB2, and CB3). The presence of the SH3 domain negatively regulates the ability of collybistin to translocate gephyrin to submembrane microaggregates in transfected mammalian cells. Because the majority of native collybistin isoforms appear to harbor the SH3 domain, this suggests that collybistin activity may be regulated by protein-protein interactions at the SH3 domain. We localized the binding sites for collybistin and the GlyR β subunit to the C-terminal MoeA homology domain of gephyrin and show that multimerization of this domain is required for collybistin-gephyrin and GlyR-gephyrin interactions. We also demonstrate that gephyrin clustering in recombinant systems and cultured neurons requires both collybistin-gephyrin interactions and an intact collybistin pleckstrin homology domain. The vital importance of collybistin for inhibitory synaptogenesis is underlined by the discovery of a mutation (G55A) in exon 2 of the human collybistin gene (ARHGEF9) in a patient with clinical symptoms of both hyperekplexia and epilepsy. The clinical manifestation of this collybistin missense mutation may result, at least in part, from mislocalization of gephyrin and a major GABAAreceptor subtype.
Proteolytic Stress Causes Heat Shock Protein Induction, Tau Ubiquitination, and the Recruitment of Ubiquitin to Tau-Positive Aggregates in Oligodendrocytes in Culture
Authors: Goldbaum Olaf , Richter-Landsberg Christiane
Published: June 2004

Molecular chaperones and the ubiquitin-proteasome system are participants in the defense against unfolded proteins and provide an effective protein quality control system that is essential for cellular functions and survival. Ubiquitinated tau-positive inclusion bodies containing the small heat shock protein αB-crystallin in oligodendrocytes are consistent features of a variety of neurodegenerative diseases, and defects in the proteasome system might contribute to the aggregation process. Oligodendrocytes, the myelin-forming cells of the CNS, are specifically sensitive to stress situations. Here we can show that in cultured rat brain oligodendrocytes proteasomal inhibition by MG-132 or lactacystin caused apoptotic cell death and the induction of heat shock proteins in a time- and concentration-dependent manner. Specifically, αB-crystallin was upregulated, and ubiquitinated proteins accumulated. After incubation with MG-132 the tau was dephosphorylated, which enhanced its microtubule-binding capacity. Proteasomal inhibition led to ubiquitination of tau and its association with αB-crystallin and to the occurrence of thioflavine S-positive aggregates in the oligodendroglial cytoplasm. These aggregates were positive for tau and also contained ubiquitin and αB-crystallin; hence they resembled the glial cytoplasmic inclusions observed in white matter disease and frontotemporal dementias with parkinsonism linked to chromosome 17 (FTDP-17). In summary, the data underscore the specific sensitivity of oligodendrocytes to stress situations and point to a causal relationship of proteasomal impairment and inclusion body formation.
Glial Glutamate Transporters Limit Spillover Activation of Presynaptic NMDA Receptors and Influence Synaptic Inhibition of Purkinje Neurons
Authors: Huang Hao , Bordey Angélique
Published: June 2004

Glutamate transporters limit cross talk between excitatory synapses by removing synaptically released glutamate. However, the role of glutamate transporters in limiting the action of synaptically released glutamate at inhibitory synapses remains unknown. Single and paired whole-cell patch-clamp recordings were obtained from Purkinje neurons and Bergmann glia in mouse cerebellar slices to determine the function of neuronal and glial glutamate transporters at GABAergic synapses onto Purkinje neurons. NMDA and inhibition of glutamate transporters withdl-threo-β-benzyloxyaspartic acid (TBOA) increased the frequency of miniature IPSCs (mIPSCs) by enhancing presynaptic NMDA receptor (NMDAR) activation, whereas inhibition of cystine-glutamate antiporters had no effect on mIPSCs. Selective inhibition of glutamate transporters in an individual Bergmann glial cell enhanced mIPSC frequency recorded in an adjacent Purkinje neuron significantly more than did postsynaptic transporter inhibition. TBOA did not change the frequency of spontaneous IPSCs (sIPSCs) but decreased their amplitude, as well as that of evoked IPSCs (eIPSCs), and enhanced the paired-pulse ratio. The action of NMDAR activation on eIPSCs but not that on mIPSCs was prevented by 100 μmryanodine. Repetitive stimulations of climbing fibers resulted in a NMDAR-dependent reduction of sIPSC amplitude, and this effect was enhanced by TBOA even when postsynaptic glutamate transporters were blocked. These data indicate that glial glutamate transporters limit glutamate spillover from excitatory to inhibitory synapses and strongly influence synaptic inhibition of Purkinje neurons by controlling NMDAR activation on GABAergic terminals.
β2-Containing Nicotinic Receptors Contribute to the Organization of Sleep and Regulate Putative Micro-Arousals in Mice
Authors: Léna Clément , Popa Daniela , Grailhe Régis , Escourrou Pierre , Changeux Jean-Pierre , Adrien Joëlle
Published: June 2004

The cholinergic system is involved in arousal and in rapid eye movement sleep (REMS). To evaluate the contribution of nicotinic acetylcholine receptors (nAChRs) to these functions, we studied with polygraphic recordings the regulation of sleep in mice lacking the β2 subunit gene of the nAChRs, a major component of high-affinity nicotine binding sites in the brain. Nicotine (1-2 mg/kg, i.p.) increased wakefulness in wild-type but not knock-out animals, indicating that β2-containing nAChRs mediate the arousing properties of nicotine. Under normal conditions, the β2-/- mice displayed the same amounts of waking, non-REM sleep (NREMS) and REMS as their wild-type counterparts. However, they exhibited longer REMS episodes and a reduced fragmentation of NREMS by events characterized notably by a transient drop in EEG power and frequently associated with EMG activation, tentatively referred to as micro-arousals. Respiration monitoring showed that these events were accompanied with, but not caused by, breathing irregularities. Sleep deprivation of β2-/- mice resulted in a normal increase in REMS episode duration and NREMS δ power but yielded a reduction of the number of micro-arousals in NREMS. In contrast, in β2-/- mice, a 1 hr immobilization stress failed to produce the normal rebound in REMS in the following 12 hr and, instead, was associated with increased NREMS fragmentation and sustained corticosterone levels. Our results show that the β2-containing nAChRs contribute to the organization of sleep by regulating the transient phasic activity in NREMS, the REMS onset and duration, and the REMS-promoting effect of stress.
Performance of small herschel‐type venturi tubes
Authors: Walker P. L. , Foresti R. J. , Rusinko F. , McCormick B. W.
Published: June 2004

The characteristics of five Herschel‐type Venturi tubes with throat diameters ranging from 0.073 to 0.359 in, and throat‐to‐pipe—diameter ratios from 0.0882 to 0.4340 have been investigated.
Heat and mass transfer in packed beds
Authors: Plautz Donald A. , Johnstone H. F.
Published: June 2004

Eddy mass diffusivities, effective thermal conductivities, and wall heat transfer coefficients were measured in an 8‐in. tube packed with 1/2‐ and 3/4‐in. glass spheres. Superficial mass velocities ranged from 110 to 1,640 Ib./(hr.) (sq. ft.), corresponding to modified Reynolds numbers of 100 to 2,000. Air was the main stream fluid in all cases.

The modified Peclet group (DpV/E*td) was found to be constant at a value of about 12 in the region of fully developed turbulence. At lower Reynolds numbers this group varied with the flow rate. Effective thermal conductivities were correlated by an equation. Modified Peclet numbers for heat transfer were about 25% less than those for mass transfer. The wall heat transfer coefficient varied with the superficial mass velocity as hw = 0.090 (Go0.75).

An explanation is suggested for the similarity in velocity dependence between these values and those for turbulent flow in an empty tube, based on channeling at the wall.
Thermodynamic properties of l‐butene
Authors: Weber James H.
Published: June 2004

The thermodynamic properties of 1‐butene have been calculated over a temperature range of 32° to 480°F. and at pressures up to 1,000 lb./sq. in. abs. These properties were determined from vapor‐pressure, volumetric, heat‐capacity, and latent‐heat of vaporization data through the application of rigorous thermodynamic relationships. The calculated data have been found to be internally consistent. The enthalpy values are believed to be accurate to within ±0.5 B.t.u./lb. and the entropy values to ±0.0005 B.t.u./(lb.) (°R.).
Performance of packed columns. III. Holdup for aqueous and nonaqueous systems
Authors: Shulman H. L. , Ullrich C. F. , Wells N. , Proulx A. Z.
Published: June 2004

Total, static, and operating holdups have been measured for 1‐in porcelain and carbon Raschig rings and 1‐in. porcelain Berl saddles, employing aqueous solutions of calcium chloride, sorbitol, and a wetting agent as well as pure methanol and benzene. The range of variables covered by this investigation includes liquid rate, 1,000 to 10,000 1b./(hr.) (sq. ft.); viscosity, 0.6 to 185 cp.; surface tension, 23 to 86 dynes/cm.; specific gravity, 0.8 to 1.32.

Equations and charts are presented for estimating holdups for all liquids. The application of holdups for estimating mass transfer coefficients, kG, and effective interfacial areas, a, is discussed.

The total holdups for water, methanol, and benzene can be used to explain why mass transfer coefficients obtained by vaporization of pure liquids in packings seem to depend on gas diffusivity raised to the 0.15 power instead of the 0.67 power, as found in other mass transfer studies. The larger total holdups of nonaqueous liquids result in larger effective interfacial areas in the packing, which mask the effect of the change in gas diffusivity.
Fundamentals of the hydrodynamic mechanism of splitting in dispersion processes
Authors: Hinze J. O.
Published: June 2004

The splitting of globules is an important phenomenon during the final stages of disintegration processes. Three basic types of deformation of globules and six types of flow patterns causing them are distinguished.

The forces controlling deformation and breakup comprise two dimensionless groups: a Weber group NWe and a viscosity group NVi. Breakup occurs when NWe exceeds a critical value (NWe)crit. Three cases are studied in greater detail: (a) Taylor's experiments on the breakup of a drop in simple types of viscous flow, (b) breakup of a drop in an air stream, (c) emulsification in a turbulent flow.

It is shown that (NWe)crit depends on the type of deformation and on the flow pattern around the globule. For case (a) (NWe)crit shows a minimum value ∼ 0.5 at a certain value of (NVi) and seems to increase indefinitely with either decreasing or increasing ratio between the viscosites of the two phases. For case (b) (NWe)crit varies between 13 and ∞, depending on NVi and on the way in which the relative air velocity varies with time, the lowest value refers to the true shock case and Nvi→0. For case (c) (NWe)crit, which determines the maximum drop size in the emulsion, amounts to ∼1, and the corresponding values of NVi appear to be small. A formula is derived for the maximum drop size.
Diffusional film characteristics in turbulent flow: Dynamic response method
Authors: Keyes John J.
Published: June 2004

Application of a dynamic or unsteady‐state technique to the problem of radial mixing in a tube is described. Measurement of the amplitude attenuation suffered by a sinusoidally modulated gas composition wave as it flows within an open (unpacked) tube makes possible the direct determination of an “equivalent gas film thickness” from which a mass transfer film coefficient may be readily calculated.

A brief summary of the method employed for obtaining the necessary mathematical relationships is presented, along with descriptions of the techniques developed for measurement of small amplitude differences at wave frequencies as high as 10 cycles /sec.

Experimentally, conditions were varied to include a range of Schmidt number from 0.18 to 1.24 and of Reynolds number from 4,000 to 50,000. The results of this work appear to fall nearly in line with the semitheoretical equation of Martinelli as written for mass transfer. Generally speaking, a was found to be an increasing function ofNSc, varying from about 0.5 to a maximum of 0.77; β, in turn, was found to increase withNRefrom 0.3 to 0.5.

A suggestion for extending the method to measurement of eddy diffusivities in the axial direction is included.
Low‐temperature oxidation of ammonia in fixed and fluidized beds
Authors: Johnstone H. F. , Batchelor J. D. , Shen C. Y.
Published: June 2004

The oxidation of ammonia in the presence of manganous oxide‐bismuth oxide catalyst supported on small alumina spheres was studied in both fixed and fluidized beds in the temperature range from 205° to 250°C. The column used was 4½ in. in diameter and 43 in. high. The experiments were made so that the transport effects in the fluidized bed might be separated from the chemical kinetic effects.

In accordance with the theory of two‐phase fluidization proposed in a previous paper, comparison is made between the reaction rate associated with the discontinuous phase and that associated with the continuous phase as estimated from the results in the fixed bed. The over‐all reaction‐rate constants in the fluidized bed can be related to those in the fixed bed by an exponential term in the superficial gas velocity, Vn; n is a constant which depends on the reaction system and the size and type of the reactor.
Effect of void volume and prandtl modulus on heat transfer in tube banks and packed beds
Authors: Weisman Joel
Published: June 2004

A correlation is presented relating the heat transfer characteristics of cross‐flow heat exchangers to the void‐volume‐and‐tube‐pitch ratio. A similar correlation is found to be applicable to heat and mass transfer in packed and fluidized beds and through screens.

A limited amount of data has been obtained on the effect of the Prandtl modulus at high Reynolds numbers. These data seem to indicate, as do those for flow through tubes, that the Prandtl number exponent is a function of Reynolds number.
Gas‐solid contact in fluidized beds
Authors: Shen C. Y. , Johnstone H. F.
Published: June 2004

According to the concept of two‐phase fluidization, a part of the gas in a fluidized reactor passes through the uniform dispersed solid‐gas phase in the form of bubbles, channels, and slugs. Material transport by mixing or diffusion takes place at the phase boundaries. A mass transfer coefficient between the two phases may be used to evaluate the effectiveness of contact between the gas and solid. The reaction rate for the catalytic decomposition of nitrous oxide was determined in a fluidized bed of impregnated alumina particles and compared with the corresponding rate in a fixed bed. Simultaneous rate equations were established based on the assumption that the continuous phase is either completely unmixed or uniformly mixed, and the discontinuous phase passes without mixing. The effects of the velocity of the gas, the particle size, and the bed depth on the transfer coefficient were investigated. Applications to heat transfer in fluidized beds and equipment design are discussed.
Dynamics of vapor bubbles and boiling heat transfer
Authors: Forster H. K. , Zuber N.
Published: June 2004

Analytical expressions for bubble radii and growth rates derived by the authors are applied in an analysis of surface boiling at high heat transfer rates. It is shown that the product of bubble radius and radial velocity is a constant, independent of the bubble radius. This circumstance permits the formulation of a Reynolds number for the flow in the thin superheated liquid layer adjacent to the heating surface. The result of the analysis is then applied to maximal heat transfer rates in pool boiling.
A generalized correlation of diffusion coefficients
Authors: Fair J. R. , Lerner B. J.
Published: June 2004

Graphical correlations of binary gas diffusion coefficients are developed based on the Hirschfelder‐Bird‐Spotz diffusion equation and the theorem of corresponding states. A critical diffusion coefficient is defined and is used in turn for a definition of a “reduced” coefficient. The reduced diffusion coefficient is correlated graphically in generalized form in terms of the reduced properties of the diffusing gas. Using air as a reference “barrier” gas, the authors compared critical diffusion coefficients for various gases diffusing through a single barrier gas with the critical coefficients for these gases through air. This ratio, termed thebarrier gas ratio, was found to be independent of the properties of the diffusing gas. A graphical correlation of the barrier gas ratio enables rapid estimation of a binary diffusion coefficient with a minimum of information.
Correlation of bubble‐cap fractionating‐column plate efficiencies
Authors: Oliver Earl D. , Watson C. C.
Published: June 2004

A method of estimating the true conditions of operation of a bubble‐cap tray is presented. Intermediate between the Murphree and the Lewis methods, which represent the extremes of actual operation, this method involves the use of a correlation to determine the degree of liquid mixing on the tray and the use of new relations between the Murphree vapor efficiency, the Lewis case I efficiency, and the true local efficiency. For the last, partial liquid mixing is taken into account.

Data were obtained on an 18‐in. O.D. three‐tray bubble‐cap tower containing ten 3‐in. bubble caps a tray. Partial liquid mixing was correlated for changes in vapor and liquid rates, pressure, temperature, and weir height for the system ethylene dichloride‐toluene.

Efficiency data on acetone‐water, ethanol‐water, and ethylene dichloride‐toluene showed the following effects: (1) low concentration of lwo boiler usually, but not always, resulted in low true local efficiencies, always with high Murphree efficiencies; (2) vapor velocity effects are more intimately connected with slot velocity than superficial velocity (and hence entrainment); (3) raising the pressure gives higher efficiencies; (4) an increase in liquid depth increases the true local efficiency but may have no effect on the Murphree efficiency.
Mechanics of steady state single‐phase fluid displacement from porous media
Authors: Von Rosenberg D. U.
Published: June 2004

The physical processes are discussed by which a fluid is displaced from a porous medium during steady state viscous flow by another fluid of the same density and viscosity under conditions of complete miscibility of the two fluids. The displacement occurs on a microscopic scale as a result of combined convective and diffusional mixing. The length of the zone of mixing which comprises the displacement front is predicted to be dependent upon the rate of flow, the diffusion coefficient for the two‐fluid system, the characteristics of the pore geometry, and the distance the front has traversed at the time of its observation.

Experimental data are presented for the displacement of benzene by ethyl n‐butyrate at several rates of flow from packed sand columns. These data show that the length of the frontal mixing zone after a prescribed distance of flow is greater at the higher rates of flow. The postulated dependence of the length of the front upon the diffusion coefficient and the pore geometry has not yet been investigated.
Analysis of kinetic data for heterogeneous reactions
Authors: Weller Sol
Published: June 2004

The chemical engineer frequently has to correlate kinetic data for heterogeneous reactions simply and accurately in order to make useful predictions of reaction rates over a range of conditions. The Langmuir‐Hinshelwood approach, which is frequently used for this purpose, does not have the theoretical validity commonly attributed to it, and its use leads to unnecessary mathematical complexity. A simpler method of analysis is suggested which is based on power dependencies of the rate on concetrations, the powers being restricted to integral of half‐integral values. The data for several reactions are shown to be adquately correlated by the suggested procedure, which is simple and convenient.
Kinetics on ideal and real surfaces
Authors: Boudart Michel
Published: June 2004

The wide applicability of the Langmuir‐Hinshelwood classical kinetics to surfaces which are known to depart strongly from ideal Langmuir behavior is a well‐known paradox of surface catalysis. The applicability and limitations of the classical method are illustrated by means of a simple reaction. The generality of the method is demonstrated by its applicability to ammonia synthesis with and without water vapor. The limitations are often more than compensated for by the added insight into reaction mechanism which it can provide without unded complexity. A three‐step approach to surface kinetics is suggested and discussed.
Adsorption phase equilibrium correlations: Light‐hydrocarbon vapors on activated charcoal
Authors: Etherington Lewis D. , Haney Roy E. D. , Herbst Walter A. , Scheeline Harod W.
Published: June 2004

Data correlations are presented for equilibrium adsorption of pure hydrocarbon vapors and their mixtures. The systems represented are C1 to C4 hydrocarbons (olefins and paraffins) on gas‐adsorbent grades of activated charcoal. The mixture data are limited to binary and ternary gas systems. The adsorption conditions represented among the correlated data cover ranges of 77° to 175°F. temperature and 0 to 100 lb./sq. in. gauge. With the use of empirical adsorption constants, a common correlation of specific adsorption capacity for the various hydrocarbons is presented; it applies for either pure components or their mixtures. A correlation is given also for adsorption relative volatilities. Approximate adsorption heats, a limited amount of high‐temperature steam adsorption data, and sample calculations on applications of the correlations are included. The prediction methods are recommended for adsorption conditions up to 250°F. and 250 lb/sq. in. gauge for the particular systems studied.
Pressure drop through porous media
Authors: Brownell L. E. , Gami D. C. , Miller R. A. , Nekarvis W. F.
Published: June 2004

Fluid flow data are presnted for beds of uniformly sized spheres consolidated with resin over a porosity range from 36.4 to 12.3%. The data are analyzed in terms of an effective pore volume and equations are given for predicting pressure drop by use of a friction‐factor‐Reynolds‐number plot.
Hydraulic analysis of sudden flow changes in a complex pumping circuit
Authors: Alves George E.
Published: June 2004

A problem arose as to what would happen if there were sudden failures of power to one or more pumps of a large‐scale complex pumping circuit composed of several individual pumping systems. This paper describes the application of several published methods of hydraulic transient analysis to the problem. The performance of the system computed under several assumptions is discussed, and a comparison is made with experimentally determined values.
Use of zirconium in liquid‐sodium systems
Authors: Bowman F. E. , Cubicciotti D. D.
Published: June 2004

The attractive nuclear properties of zirconium make it a highly desirable core material for sodium‐cooled reactors. The elevated temperature strength while low is sufficient for certain applications. Development of higher strength alloys is underway. Sodium in itself is completely compatible with zirconium; however, the nonmetallic contaminants, namely oxygen, hydrogen, and nitrogen, can effect serious damage. The primary problem in the use of zirconium in a sodium system, then, lies in controlling these impurities in the sodium.