Longitudinal Tracks Research Articles

Learning Apart, Living Apart: How the Racial and Ethnic Segregation of Schools and Colleges Perpetuates Residential Segregation

BackgroundDespite a powerful civil rights movement and legislation barring discrimination in housing markets, residential neighborhoods remain racially segregated.PurposeThis study examines the extent to which neighborhoods’ racial composition is inherited across generations and the extent to which high schools’ and colleges’ racial composition mediates this relationship. To understand the underlying social processes responsible for racial segregation, I use the spatial assimilation model, the place stratification model, and perpetuation theory.PopulationData for this project are from the National Education Longitudinal Study (NELS), the Integrated Postsecondary Education Data System (IPEDS), and the U.S. Census.Research DesignA longitudinal design tracks the racial composition of the schools, colleges, and neighborhoods from adolescence through age 26.FindingsHolding constant the percent white in teenagers’ neighborhoods, socioeconomic status, and other variables, the percent white that students experience in high school and college has a lasting influence, affecting the percent white in young adult neighborhoods and explaining 31% of intergenerational continuity of neighborhood racial composition.ConclusionsThe analyses suggest that racial segregation in high schools and colleges reinforces racial segregation in neighborhoods.

Transcriptional control of axonal guidance and sorting in dorsal interneurons by the Lim-HD proteins Lhx9 and Lhx1

BackgroundLim-HD proteins control crucial aspects of neuronal differentiation, including subtype identity and axonal guidance. The Lim-HD proteins Lhx2/9 and Lhx1/5 are expressed in the dorsal spinal interneuron populations dI1 and dI2, respectively. While they are not required for cell fate acquisition, their role in patterning the axonal trajectory of dI1 and dI2 neurons remains incompletely understood.ResultsUsing newly identified dI1- and dI2-specific enhancers to trace axonal trajectories originating from these interneurons, we found that each population is subdivided into several distinct groups according to their axonal pathways. dI1 neurons project axons rostrally, either ipsi- or contra-laterally, while dI2 are mostly commissural neurons that project their axons rostrally and caudally. The longitudinal axonal tracks of each neuronal population self-fasciculate to form dI1- and dI2-specific bundles. The dI1 bundles are spatially located ventral relative to dI2 bundles. To examine the functional contribution of Lim-HD proteins to establishment of dI axonal projections, the Lim-HD code of dI neurons was altered by cell-specific ectopic expression. Expression of Lhx1 in dI1 neurons caused a repression of Lhx2/9 and imposed caudal projection to the caudal commissural dI1 neurons. Complementarily, when expressed in dI2 neurons, Lhx9 repressed Lhx1/5 and triggered a bias toward rostral projection in otherwise caudally projecting dI2 neurons, and ventral shift of the longitudinal axonal fascicule.ConclusionThe Lim-HD proteins Lhx9 and Lhx1 serve as a binary switch in controlling the rostral versus caudal longitudinal turning of the caudal commissural axons. Lhx1 determines caudal turning and Lhx9 triggers rostral turning.

Public—Nonprofit Partnership

This longitudinal study tracks the generation of trust between a public agency and nine community-based nonprofits (CBNs) over a 10-year period. The evolution from active distrust to trust was demonstrated by the generation of ideological consensus and domain consensus achieved through sharing information, integrated responsibilities and authority, and collaborative decision making. Results indicate that public—nonprofit partnerships create a locus for the practice of the New Public Service. CBNs offer public administrators a bridge into disenfranchised communities and a point of engagement where partners join public agency resources and expertise with tacit knowledge of community through a trusted institution.

Different mechanisms of saturated versus polyunsaturated FFA-induced apoptosis in human endothelial cells

Apoptosis and underlying mechanisms were evaluated in human umbilical vein endothelial cells (HUVECs), in target tissues of late diabetic vascular complications [human aortic endothelial cells (HAECs) and human retinal endothelial cells (HRECs)], and in endothelial progenitor cells (EPCs) exposed to FFAs, which are elevated in obesity and diabetes. Saturated stearic acid concentration dependently induced apoptosis that could be mediated via reduced membrane fluidity, because both apoptosis and membrane rigidity are counteracted by eicosapentaenoic acid. PUFAs triggered apoptosis at a concentration of 300 micromol/l in HUVECs, HAECs, and EPCs, but not HRECs, and, in contrast to stearic acid, involved caspase-8 activation. PUFA-induced apoptosis, but not stearic acid-induced apoptosis, strictly correlated (P < 0.01) with protein expression of E2F-1 (r = 0.878) and c-myc (r = 0.966). Lack of c-myc expression and activity owing to quiescence or transfection with dominant negative In373-Myc, respectively, renders HUVECs resistant to PUFA-induced apoptosis. Because c-myc is abundant in growing cells only, apoptosis triggered by PUFAs, but not by saturated stearic acid, obviously depends on the growth/proliferation status of the cells. Finally, this study shows that FFA-induced apoptosis depends on the vascular origin and growth/proliferation status of endothelial cells, and that saturated stearic acid-induced apoptosis and PUFA-induced apoptosis are mediated via different mechanisms.

Orthopaedic In-Training Examination Performance: A Nine-Year Review of a Residency Program Database

The Orthopaedic In-Training Examination (OITE) provides an objective way for both the residency program and the resident to monitor progress. This longitudinal descriptive study tracks the OITE performance of 16 residents from one orthopaedic surgery residency program over nine years (1997-2005). Domain comparisons are made to national averages (N > 3000) by mean difference and split middle celeration line assessment trend analysis to evaluate program strengths and weaknesses. Further evaluation by postgraduate year (PGY) is made of domains that were deemed to be in need of moderate attention. Resident performance for the medically related issues, rehabilitation, and sports medicine domains were deemed acceptable. Resident performance on the orthopaedic science, orthopaedic diseases, hip and knee reconstruction, spine, and shoulder and elbow domains were deemed to be in need of minor attention. Musculoskeletal trauma, pediatric orthopaedics, foot and ankle, and hand domains were deemed to be in need of moderate attention. Further analysis of these domains by PGY revealed less positive slopes for the pediatric orthopaedics and musculoskeletal trauma domains, and a negative slope for the hand domain between PGY-3 and PGY-4, each indicative of lower domain-specific OITE scores than the national mean. A similar, less positive slope was identified between PGY-2 and PGY-3 for the foot and ankle domain. A longitudinal descriptive review of orthopaedic surgery resident OITE performance enables the departmental education committee to identify curricular content areas that require attention, select the most efficient modes of educational information delivery, facilitate learning through the application of innovative educational technologies, establish measurable educational program goals, and more prescriptively allocate personnel and equipment resources.

Longitudinal Educational Tracks in an Emergency Medicine Residency Curriculum

Longitudinal Educational Tracks in an Emergency Medicine Residency Curriculum

Airborne laser altimetry survey of Glaciar Tyndall, Patagonia

The first airborne laser altimetry measurements of a glacier in South America are presented. Data were collected in November of 2001 over Glaciar Tyndall, Torres del Paine National Park, Chilean Patagonia, onboard a Twin Otter airplane of the Chilean Air Force. A laser scanner with a rotating polygon-mirror system together with an Inertial Navigation System (INS) were fixed to the floor of the aircraft, and used in combination with two dual-frequency GPS receivers. Together, the laser–INS–GPS system had a nominal accuracy of 30 cm after data processing. On November 23rd, a total of 235 km were flown over the ablation area of Glaciar Tyndall, with 5 longitudinal tracks with a mean swath width of 300 m, which results in a point spacing of approximately 2 m both along and across track. A digital elevation model (DEM) generated using the laser altimetry data was compared with a DEM produced from a 1975 map (1:50,000 scale — Instituto Geográfico Militar (IGM), Chile). A mean thinning of − 3.1 ± 1.0 m a − 1 was calculated for the ablation area of Glaciar Tyndall, with a maximum value of − 7.7 ± 1.0 m a − 1 at the calving front at 50 m a.s.l. and minimum values of between − 1.0 and − 2.0 ± 1.0 m a − 1 at altitudes close to the equilibrium line altitude (900 m a.s.l.). The thinning rates derived from the airborne survey were similar to the results obtained by means of ground survey carried out at ∼ 600 m of altitude on Glaciar Tyndall between 1975 and 2002, yielding a mean thinning of − 3.2 m a − 1 [Raymond, C., Neumann, T.A., Rignot, E., Echelmeyer, K.A., Rivera, A., Casassa, G., 2005. Retreat of Tyndall Glacier, Patagonia, over the last half century. Journal of Glaciology 173 (51), 239–247.]. A good agreement was also found between ice elevation changes measured with laser data and previous results obtained with Shuttle Radar Topography Mission (SRTM) data. We conclude that airborne laser altimetry is an effective means for accurately detecting glacier elevation changes in Patagonia, where an ice thinning acceleration trend has been observed during recent years, presumably in response to warming and possibly also drier conditions.

The Study of Exceptional Talent

The Study of Exceptional Talent (SET) identifies students who exhibit extremely advanced mathematical and/or verbal reasoning abilities and helps them find the challenging educational programs they need to achieve their full potential. Specifically, students who score 700–800 on the mathematical or verbal portion of SAT I before the age of 13 are invited to take advantage of SET's counseling and mentoring opportunities. An ongoing longitudinal study tracks the progress of these students, and their achievements to date have been exceptional. SET students, as a group, participate in a variety of accelerated programs, attend highly selective colleges and universities and earn advanced degrees in large numbers. Those who have embarked on their careers appear to be excelling in their chosen fields as well.

Information Politics and Information Culture: A Case Study

This article introduces the concepts of information politics and information culture and presents a case study that explores these concepts. The literature from the areas of IS theory and organization theory that provides a backdrop to these concepts is discussed. A case of an organization that has characteristics of both small business and voluntary organization is presented as initial validation of the concepts of information politics and information culture. The case draws on a longitudinal interpretivist study and tracks a trajectory of organizational design, information politics, information culture, management and organizational performance over 25 months. The primary finding is that the organization studied exhibited two distinct information politics and information cultures, each related to different development phases—the era of clan and the era of teams. The article also discusses particular aspects of information politics and information culture and how these relate to organizational performance. Derived are implications for further research on information politics and information culture as well as for a broader parent framework called Information View of Organization.

Going Public: The Emergence and Effects of Soft Bureaucracy Within a Knowledge-Intensive Firm

The aim of this paper is to explore and explain the emergence over time of forms of organization and governance (referred to as ‘ organizing templates’) in a knowledge-intensive firm (KIF). A longitudinal case study tracks the ways in which this firm has evolved from its inception in 1986 through to 2001. The analysis emphasizes, in particular, the strategic role of power politics in shaping organizing templates following firm success and expansion. The paper focuses on the shift away from adhocracy as the (ideological) organizing template and towards a new form of governance within the firm, characterized as soft bureaucracy. It shows how this shift coincides with economic, technological and cultural imperatives imposed by the increased sovereignty of the market. A multilevel analytical model of organizational change processes is outlined in which shifting dominant management logics are aligned with firm level innovations through organizing templates. This framework is used to structure our narrative historical account of the various phases of restructuring throughout the period. The paper attempts to inform existing understanding of soft bureaucracy by showing how this particular form of governance emerges in a KIF through the interplay between macro-level sectoral change and micro-political processes. It concludes by considering first the implications of this shift for firm level knowledge work processes, and second, the politics of organizational change more generally in the knowledge-intensive sector at the start of the 21st century.

Erase band width evaluation by phase coherency

As the track density increases, the properties of the erase band and track edge become more and more important. In this study, we report on a pertinent erase band measurement method, based on a magnetic force microscope, to characterize the erase bands and track edge overwrite properties resulting from the write-head fringe field in a precise manner. The erase bands of written tracks were measured by using the proposed technique, the so-called phase coherency method, for both longitudinal recording tracks and perpendicular tracks in comparison to the amplitude technique.

The CNS Midline Cells Coordinate Proper Cell Cycle Progression and Identity Determination of the Drosophila Ventral Neuroectoderm

The CNS midline cells, specified by the single-minded (sim) gene, are required for the proper patterning of the ventral CNS and epidermis, which are derived from the Drosophila ventral neuroectoderm. Defects in the sim mutant are characterized by the loss of the gene expression, which is required for the proper formation of the ventral neurons and epidermis, and by a decrease in the spacing of longitudinal and commissural axon tracks. Molecular and cellular mechanisms for these defects were analyzed to elucidate the precise role of the CNS midline cells in proper patterning of the ventral neuroectoderm during embryonic neurogenesis. These analyses showed that the ventral neuroectoderm in the sim mutant fails to carry out its proper formation and characteristic cell division cycle. This resulted in the loss of the dividing neuroectodermal cells that are located ventral to the CNS midline. The CNS midline cells are also required for the cell cycle-independent expression of the neural and epidermal markers. This indicates that the CNS midline cells are essential for the establishment and maintenance of the ventral epidermal and neuronal cell lineage by cell–cell interaction. On the other hand, the CNS midline cells do not cause extensive cell death in the ventral neuroectoderm. This study indicates that the CNS midline cells play important roles in the coordination of the proper cell cycle progression and the correct identity determination of the adjacent ventral neuroectoderm along the dorsoventral axis.

Increasing track density in a multitrack magnetic recording system by crosstalk compensation and track following

A matrix thin film writing head and a magneto-optic readout system have been developed. They can write and read simultaneously more than 1000 parallel longitudinal tracks on a tape with high areal bit density. Such longitudinal recording systems are usually limited in track density by the intertrack interference and guiding errors in the tape transport. A simple transversal filtering over the tracks to remove intertrack interference and the behavior of a very simple and efficient optical track following servomechanism are presented. Both exploit correlations between tracks. Each track is identified by its own mean value that has been fixed at coding.

On The Divergence Buckling Of A Wide Bandsaw Plate By Roll-tensioning

Residual membrane stresses are induced in wide bandsaw plates by cold-rolling longitudinal tracks, a process known as roll-tensioning. When properly done, roll-tensioning substantially improves the cutting performance of the bandsaw. However, excessive rolling can buckle the plate causing rubbing of the plate against the work piece. The analysis in this paper shows that excessive roll-tensioning induces transverse or torsional buckling of the plate, depending on the location of the longitudinal tracks across the plate width and the magnitude of the uniform longitudinal (axial) tension applied to the plate during the cutting operation. The buckling modes are characterized by a number of waves along the length of the plate that are qualitatively predictable by theory.

Collagen-associated sulphated proteoglycans. Ultrastructure after formaldehyde-cetylpyridinium chloride fixation

In the course of an ultrastructural cytochemical study of intracellular sulphated proteoglycans involving the addition of cetylpyridinium chloride in the primary aldehyde fixative, a remarkable ultrastructural preservation of the collagen-associated sulphated proteoglycans was observed. Together with the preservation of their localization among the collagen fibrils (with, for some of them, a 50 nm periodic association with d-bands) and of their native elongated shape, previously observed under similar technical conditions, these stick-shaped and chondroitinase ABC-sensitive proteoglycans exhibited a typical pattern with several dense longitudinal parallel tracks (periodicity: 3-4 nm) not described as yet. Readily observable without high iron diamine-staining, the morphology of these cetylpyridinium chloride-precipitated and collagen-associated polyanions was particularly enhanced after incubation in the diamine solution which ascertained their sulphate content. Such a common ultrastructural organization with parallel tracks for both intracellular (i.e., in eosinophilic polymorphonuclear cells and Kurloff cells) and extracellular CPC-precipitated sulphated proteoglycans could correspond to intrinsic properties of the complexed molecules and could be related to 'double track' proteoglycans observed under other technical conditions in basement membranes.

Reendothelialization and maintenance of endothelial integrity in longitudinal denuded tracks in the thoracic aorta of rats

Endothelial repair was studied during, and up to 26 weeks following reendothelialization of longitudinal tracks denuded of endothelium. Deendothelialized tracks were produced on the ventral aspect of the thoracic aortas of rats. A standardized denudation procedure was used in conjunction with continuous intravenous infusion of [ 3H]thymidine to obtain quantitative evaluations of replication, migration, and cell density. The method of denudation was relatively gentle, selective, and reproducible. Reendothelialization was completed in < 66 h. During reendothelialization, cell migration and replication proceeded simultaneously until confluence was reached. Following confluence, as migration ceased, cell density returned toward control levels. It continued to rise, associated with continued, though attenuated, nuclear incorporation of [ 3H]thymidine, until it reached 1 1 2 –2 1 2 times that of adjacent uninjured control endothelium. The boundaries, or margins, of the tracks were well demarcated as judged by the pattern of labeled cells within and unlabeled cells adjacent to reendothelialized tracks. Widths of deendothelialized and reendotheliazed tracks were similar. Thus, endothelial cells in uninjured regions surrounding denuded tracks were not observed to contribute to reendothelialization by proliferation. During reendothelialization, unlabeled cells were observed within reendothelializing tracks. Thus, some cells migrated relatively long distances (0.3 – 0.4 mm) before either replicating or sloughing from the luminal surface. Endothelial cell density within reendothelialized tracks remained elevated at 12 and 26 weeks following denudation. At 12 weeks there was little intermingling of cells inside tracks (labeled during reendothelialization) with unlabeled cells in adjacent uninjured areas. At 26 weeks, after a terminal 12-day continuous labeling period in previously unlabeled animals, replication of cells inside tracks was far less than that in adjacent uninjured endothelium. Thus, the newly regenerated cell population in tracks remained synchronously quiescent and physically segregated for long periods of time, despite normally occurring hemodynamic and remodeling factors which might be expected to favor continuous cell turnover and migration. Our findings relating to endothelial cell migration and replication during reendothelialization vary somewhat from those reported using other methods of deendothelialization.