Showing papers by "University of Southern California published in 1996"

Assessing the Work Environment for Creativity

Abstract: We describe the development and validation of a new instrument, KEYS: Assessing the Climate for Creativity, designed to assess perceived stimulants and obstacles to creativity in organizational work environments. The KEYS scales have acceptable factor structures, internal consistencies, test-retest reliabilities, and preliminary convergent and discriminant validity. A construct validity study shows that perceived work environments, as assessed by the KEYS scales, discriminate between high-creativity projects and low-creativity projects; certain scales discriminate more strongly and consistently than others. We discuss the utility of this tool for research and practice.

Guanxi: Connections As Substitutes for Formal Institutional Support

Abstract: Interview data from China are used to test an argument that executives develop personal connections in societies with underdeveloped legal support for private businesses. In China, such connections...

Social structural characteristics of psychological empowerment

Abstract: A set of hypotheses based on emerging theory on high-involvement systems describes expected relationships between social structural characteristics at the level of the work unit (perceptions of role ambiguity, span of control, sociopolitical support, access to information and resources, and work unit climate) and feelings of empowerment. The hypotheses are examined with data on a sample of middle managers from diverse units of a Fortune 50 organization. A work unit with little role ambiguity, strong sociopolitical support, access to information, and a participative unit climate is found to be associated with managerial perceptions of empowerment, as is working for a boss who has a wide span of control.

Fractures of the acetabulum: accuracy of reduction and clinical results in patients managed operatively within three weeks after the injury.

Abstract: The results were reviewed for 259 patients who had open reduction and internal fixation of 262 displaced acetabular fractures within twenty-one days after the injury. Two hundred and fifty-five hips were followed for a mean of six years (range, two to fourteen years) after the injury; the remaining seven, which clearly had a poor result, were followed for less than two years. According to the classification of Letournel and Judet, associated fracture types accounted for 208 (79 per cent) of the fractures, with both-column fractures being the most common type (ninety-two hips; 35 per cent). Two hundred and fifty-eight hips were operated on with a single operative approach (Kocher-Langenbeck, ilioinguinal, or extended iliofemoral). The four remaining hips were operated on with a Kocher-Langenbeck as well as an ilioinguinal approach. The reduction was graded as anatomical in 185 hips (71 per cent). The rate of anatomical reduction decreased with increases in the complexity of the fracture, the age of the patient, and the interval between the injury and the reduction. The over-all clinical result was excellent for 104 hips (40 per cent), good for ninety-five (36 per cent), fair for twenty-one (8 per cent), and poor for forty-two (16 per cent). The clinical result was related closely to the radiographic result. The clinical result was adversely affected by associated injuries of the femoral head, an older age of the patient, and operative complications. It was positively affected by an anatomical reduction and postoperative congruity between the femoral head and the acetabular roof. Osteonecrosis of the femoral head was noted in eight hips (3 per cent), and progressive wear of the femoral head was seen in thirteen (5 per cent). Subsequent operations included a total replacement of seventeen hips (6 per cent), an arthrodesis in four (2 per cent), and excision of ectopic bone in twelve (5 per cent). These findings indicate that in many patients who have a complex acetabular fracture the hip joint can be preserved and post-traumatic osteoarthrosis can be avoided if an anatomical reduction is achieved. An increase in the rate of anatomical reduction and a decrease in the rate of operative complications should be the goals of surgeons who treat these fractures.

Molecular Cloning and Disease Association of Hepatitis G Virus: A Transfusion-Transmissible Agent

Abstract: An RNA virus, designated hepatitis G virus (HGV), was identified from the plasma of a patient with chronic hepatitis. Extension from an immunoreactive complementary DNA clone yielded the entire genome (9392 nucleotides) encoding a polyprotein of 2873 amino acids. The virus is closely related to GB virus C (GBV-C) and distantly related to hepatitis C virus, GBV-A, and GBV-B. HGV was associated with acute and chronic hepatitis. Persistent viremia was detected for up to 9 years in patients with hepatitis. The virus is transfusion-transmissible. It has a global distribution and is present within the volunteer blood donor population in the United States.

A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean

Abstract: The seeding of an expanse of surface waters in the equatorial Pacific Ocean with low concentrations of dissolved iron triggered a massive phytoplankton bloom which consumed large quantities of carbon dioxide and nitrate that these microscopic plants cannot fully utilize under natural conditions. These and other observations provide unequivocal support for the hypothesis that phytoplankton growth in this oceanic region is limited by iron bioavailability.

The Current State of Solar Modeling

Abstract: Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations.

Knowledge, Strategy, and the Theory of the Firm

Abstract: This paper argues that firms have particular institutional capabilities that allow them to protect knowledge from expropriation and imitation more effectively than market contracting. I argue that it is these generalized institutional capabilities that allow firms to generate and protect the unique resources and capabilities that are central to the strategic theory of the firm.

Localization of grasp representations in humans by positron emission tomography. 2. Observation compared with imagination.

Abstract: Positron emission tomography imaging of cerebral blood flow was used to localize brain areas involved in the representation of hand grasping movements. Seven normal subjects were scanned under three conditions. In the first, they observed precision grasping of common objects performed by the examiner. In the second, they imagined themselves grasping the objects without actually moving the hand. These two tasks were compared with a control task of object viewing. Grasp observation activated the left rostral superior temporal sulcus, left inferior frontal cortex (area 45), left rostral inferior parietal cortex (area 40), the rostral part of left supplementary motor area (SMA-proper), and the right dorsal premotor cortex. Imagined grasping activated the left inferior frontal (area 44) and middle frontal cortex, left caudal inferior parietal cortex (area 40), a more extensive response in left rostral SMA-proper, and left dorsal premotor cortex. The two conditions activated different areas of the right posterior cerebellar cortex. We propose that the areas active during grasping observation may form a circuit for recognition of hand-object interactions, whereas the areas active during imagined grasping may be a putative human homologue of a circuit for hand grasping movements recently defined in nonhuman primates. The location of responses in SMA-proper confirms the rostrocaudal segregation of this area for imagined and real movement. A similar segregation is also present in the cerebellum, with imagined and observed grasping movements activating different parts of the posterior lobe and real movements activating the anterior lobe.

Bedrock incision, rock uplift and threshold hillslopes in the northwestern Himalayas

Abstract: The topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion. Dating of abandoned river-cut surfaces in the northwestern Himalayas reveals that the Indus river incises through the bedrock at extremely high rates (2–12 mm yr-1). In the surrounding mountains, the average angles of hillslopes are steep and essentially independent of erosion rate, suggesting control by a common threshold process. In this rapidly deforming region, an equilibrium is maintained between bedrock uplift and river incision, with landsliding allowing hillslopes to adjust efficiently to rapid river down-cutting.

The PIM architecture for wide-area multicast routing

Abstract: The purpose of multicast routing is to reduce the communication costs for applications that send the same data to multiple recipients. Existing multicast routing mechanisms were intended for use within regions where a group is widely represented or bandwidth is universally plentiful. When group members, and senders to those group members, are distributed sparsely across a wide area, these schemes are not efficient; data packets or membership report information are occasionally sent over many links that do not lead to receivers or senders, respectively. We have developed a multicast routing architecture that efficiently establishes distribution trees across wide area internets, where many groups will be sparsely represented. Efficiency is measured in terms of the router state, control message processing, and data packet processing, required across the entire network in order to deliver data packets to the members of the group. Our protocol independent multicast (PIM) architecture: (a) maintains the traditional IP multicast service model of receiver-initiated membership, (b) supports both shared and source-specific (shortest-path) distribution trees, (c) is not dependent on a specific unicast routing protocol, and (d) uses soft-state mechanisms to adapt to underlying network conditions and group dynamics. The robustness, flexibility, and scaling properties of this architecture make it well-suited to large heterogeneous internetworks.

A hierarchical internet object cache

Abstract: This paper discusses the design and performance of a hierarchical proxy-cache designed to make Internet information systems scale better. The design was motivated by our earlier trace-driven simulation study of Internet traffic. We challenge the conventional wisdom that the benefits of hierarchical file caching do not merit the costs, and believe the issue merits reconsideration in the Internet environment. The cache implementation supports a highly concurrent stream of requests. We present performance measurements that show that our cache outperforms other popular Internet cache implementations by an order of magnitude under concurrent load. These measurements indicate that hierarchy does not measurably increase access latency. Our software can also be configured as a Web-server accelerator; we present data that our httpd-accelerator is ten times faster than Netscape's Netsite and NCSA 1.4 servers. Finally, we relate our experience fitting the cache into the increasingly complex and operational world of Internet information systems, including issues related to security, transparency to cache-unaware clients, and the role of file systems in support of ubiquitous wide-area information systems.

Polymerase chain reaction detection of 8 putative periodontal pathogens in subgingival plaque of gingivitis and advanced periodontitis lesions

Abstract: A 16S rRNA-based polymerase chain reaction (PCR) detection method was used to determine the prevalence of Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Campylobacter rectus, Eikenella corrodens, Porphyromonas gingivalis, Prevotella intermedia. Prevotella nigrescens and Treponema denticola in subgingival specimens of 50 advanced periodontitis, 50 adult gingivitis and 50 pediatric gingivitis subjects. The optimal PCR conditions were determined for each study species. Agarose gel electrophoresis of PCR products from each study species revealed a single band of the predicted size. Restriction enzyme digestion of amplicons confirmed the specificity of the amplification. PCR detection limits were in the range of 25-100 cells. No cross-reactivity with other oral micro-organisms or nonspecific amplification was observed. The prevalence by PCR in advanced periodontitis, adult gingivitis and pediatric gingivitis subjects was 30%, 14% and 14% for A. actinomycetemcomitans, 86%, 18% and 8% for B. forsythus, 74%, 52% and 78% for C. rectus, 80%, 70% and 66% for E. corrodens, 70%, 10% and 14% for P. gingivalis, 58%, 12% and 18% for P. intermedia, 52%, 20% and 22% for P. nigrescens, and 54%, 16% and 16% for T. denticola, respectively. The prevalence was higher in the advanced periodontitis group than in both adult gingivitis and pediatric gingivitis for A. actinomycetemcomitans, B. forsythus, P. gingivalis, P. intermedia, P. nigrescens and T. denticola at P < 0.01, and for E. corrodens at P < 0.05. The prevalence of C. rectus was significantly higher in the advanced periodontitis group than in the adult gingivitis group at P < 0.01. Matching results between PCR and culture occurred in 28% (B. forsythus) to 71% (A. actinomycetemcomitans) of the samples; the major discrepancy occurred in the PCR-positive/culture-negative category. Matching results between PCR and DNA probe methods were found in 84% of the subjects (B. forsythus) and 70% (P. gingivalis). Odds ratio analysis revealed statistically significant positive associations between 17 of the 28 possible combinations (P < 0.01). This study demonstrated the utility of a 16S rRNA-based PCR detection method for identifying important subgingival microorganisms. The results indicated a strong association between the study species and periodontitis. Several previously unreported symbiotic relationships were found between the 8 species tested.

The Art of Systems Architecting

Abstract: The design of complex systems is viewed as a blend of the art of architecture with the science of engineering. The principles of systems are discussed, with examples to illustrate each point. The artistic elements of architecture are then considered, and four methods in common use, depending on the nature and phase of the project, the particular problem to be solved, and the style of the architect, are described. The role of architecting throughout the system development cycle is examined. Architecting and concurrent engineering are compared and seem to be complementary strategies. >

Organization of projections from the medial nucleus of the amygdala: a PHAL study in the rat

Abstract: The organization of axonal projections from the basomedial nucleus of the amygdala (BMA) was examined with the Phaseolus vulgaris leucoagglutinin (PHAL) method in adult male rats. The anterior and posterior parts of the BMA, recognized on cytoarchitectonic grounds, display very different projection patterns. Within the amygdala, the anterior basomedial nucleus (BMAa) heavily innervates the central, medial, and anterior cortical nuclei. In contrast, the posterior basomedial nucleus (BMAp) sends a dense projection to the lateral nucleus, and to restricted parts of the central and medial nuclei. Extra-amygdalar projections from the BMA are divided into ascending and descending components. The former end in the cerebral cortex, striatum, and septum. The BMAa mainly innervates olfactory (piriform, transitional) and insular areas, whereas the BMAp also innervates inferior temporal (perirhinal, ectorhinal) and medial prefrontal (infralimbic, prelimbic) areas and the hippocampal formation. Within the striatum, the BMAa densely innervates the striatal fundus, whereas the nucleus accumbens receives a heavy input from the BMAp. Both parts of the BMA send massive projections to distinct regions of the bed nuclei of the stria terminalis. Descending projections from the BMA end primarily in the hypothalamus. The BMAa sends a major input to the lateral hypothalamic area, whereas the BMAp innervates the ventromedial nucleus particularly heavily. Injections were also placed in the anterior cortical nucleus (COAa), a cell group superficially adjacent to the BMAa. PHAL-labeled axons from this cell group mainly ascend into the amygdala and olfactory areas, and descend into the thalamus and lateral hypothalamic area. Based on connections, the COAa and BMAa are part of the same functional system. The results suggest that cytoarchitectonically distinct anterior and posterior parts of the BMA are also hodologically distinct and form parts of distinct anatomical circuits probably involved in mediating different behaviors (for example, feeding and social behaviors vs. emotion-related learning, respectively).

Involvement of mouse Mlh1 in DNA mismatch repair and meiotic crossing over.

Abstract: Mice that are deficient in either the Pms2 or Msh2 DNA mismatch repair genes have microsatellite instability and a predisposition to tumours. Interestingly, Pms2–deficient males display sterility associated with abnormal chromosome pairing in meiosis. Here mice deficient in another mismatch repair gene, Mlh1, possess not only microsatellite instability but are also infertile (both males and females). Mlh 1 –deficient spermatocytes exhibit high levels of prematurely separated chromosomes and arrest in first division meiosis. We also show that Mlh1 appears to localize to sites of crossing over on meiotic chromosomes/Together these findings suggest that Mlh1 is involved in DNA mismatch repair and meiotic crossing over.

Collaborative Communication in Interfirm Relationships: Moderating Effects of Integration and Control:

Abstract: Governance strategies, such as integration or control, structure and regulate the conduct of parties in exchange relationships; as such, they serve to constrain the latitude of the decision making ...

The seroepidemiology of human herpesvirus 8 (kaposi’s sarcoma-associated herpesvirus): distribution of infection in ks risk groups and evidence for sexual transmission

Abstract: Striking differences in Kaposi's sarcoma (KS) risk for AIDS patients who acquire HIV via homosexual activity and those whose HIV infections derive from blood product exposure suggest the presence of a sexually transmitted agent other than HIV in the development of KS Using an immunofluorescence assay, we examined serum samples from 913 patients for the presence of antibody specific for infection by human herpesvirus 8 (HHV8), an agent whose genome is regularly found in KS tissue The distribution of HHV8 seropositivity conforms to that expected for a sexually transmitted pathogen and tracks closely with the risk for KS development Our data support the inference that this virus is the etiologic cofactor predicted by the epidemiology of KS

Sudden Cardiac Death Triggered by an Earthquake

Abstract: Background The earthquake that struck the Los Angeles area at 4:31 a.m. on January 17, 1994, was one of the strongest earthquakes ever recorded in a major city in North America. Once the life-threatening situation was over, the Northridge earthquake, so called because its epicenter was near Northridge, California, just north of Los Angeles, provided investigators an unusual opportunity to examine the relation between emotional stress and sudden cardiac death. Methods We reviewed the records of the Department of Coroner of Los Angeles County for the week before the earthquake, the day of the earthquake, the six days after the earthquake, and corresponding control periods in 1991, 1992, and 1993. Results On the day of the earthquake, there was a sharp increase in the number of sudden deaths from cardiac causes that were related to atherosclerotic cardiovascular disease, from a daily average (±SD) of 4.6±2.1 in the preceding week to 24 on the day of the earthquake (z = 4.41, P<0.001). Sixteen victims of sudd...

GRIP1, a novel mouse protein that serves as a transcriptional coactivator in yeast for the hormone binding domains of steroid receptors.

Abstract: The yeast two-hybrid system was used to isolate a clone from a 17-day-old mouse embryo cDNA library that codes for a novel 812-aa long protein fragment, glucocorticoid receptor-interacting protein 1 (GRIP1), that can interact with the hormone binding domain (HBD) of the glucocorticoid receptor. In the yeast two-hybrid system and in vitro, GRIP1 interacted with the HBDs of the glucocorticoid, estrogen, and androgen receptors in a hormone-regulated manner. When fused to the DNA binding domain of a heterologous protein, the GRIP1 fragment activated a reporter gene containing a suitable enhancer site in yeast cells and in mammalian cells, indicating that GRIP1 contains a transcriptional activation domain. Overexpression of the GRIP1 fragment in mammalian cells interfered with hormone-regulated expression of mouse mammary tumor virus-chloramphenicol acetyltransferase gene and constitutive expression of cytomegalovirus-beta-galactosidase reporter gene, but not constitutive expression from a tRNA gene promoter. This selective squelching activity suggests that GRIM can interact with an essential component of the RNA polymerase II transcription machinery. Finally, while a steroid receptor HBD fused with a GAL4 DNA binding domain did not, by itself, activate transcription of a reporter gene in yeast, coexpression of this fusion protein with GRIP1 strongly activated the reporter gene. Thus, in yeast, GRIP1 can serve as a coactivator, potentiating the transactivation functions in steroid receptor HBDs, possibly by acting as a bridge between HBDs of the receptors and the basal transcription machinery.

Transdifferentiated retinal pigment epithelial cells are immunoreactive for vascular endothelial growth factor in surgically excised age-related macular degeneration-related choroidal neovascular membranes

Abstract: Purpose To determine the cellular origin and the vascular endothelial growth factor (VEGF) immunoreactivity of the nonvascular stromal cells in surgically excised age-related macular degeneration (ARMD)-associated choroidal neovascular membranes (CNVMs). Methods Immunohistochemical analysis was performed on frozen sections of eight surgically excised ARMD-related CNVMs. Results Cytokeratin-positive, smooth muscle actin-positive polygonal or fibroblastic (transdifferentiated RPE) cells were the principal nonvascular stromal cells detected. The polygonal cells were more commonly found in active (highly vascularized) regions and were strongly immunoreactive for VEGF. The fibroblastic cells were predominantly found in fibrotic (hypovascular) regions and were minimally immunoreactive for VEGF. Conclusions Transdifferentiated RPE cells are the principal nonvascular stromal cells of both vascular and fibrotic ARMD-related CNVMs. Preferential localization of VEGF immunoreactivity with the cytoplasm of the polygonal transdifferentiated RPE cells in the highly vascularized regions of the surgically excised CNVMs suggests an important angiogenic role of these cells and this growth factor in the progression of ARMD-related choroidal neovascularization.

The effects of corporate restructuring on aggregate industry specialization

Abstract: It has been widely argued that the purpose of corporate restructuring during the 1980s was to produce a population of more industry-specialized, competitive firms in response to intensifying global competition. A number of studies show that corporate restructuring resulted in increased corporate focus during the 1980s. However, no study has yet examined whether corporate restructuring resulted in increased specialization at the industry level during the 1980s. This study examines this issue. First, we examine whether or not aggregate industry specialization increased during the 1980s. That is, we ask: did the average firm in any given U.S. industry become more or less specialized to that industry during the 1980s? Second, we examine whether corporate restructuring was a significant determinant of change in aggregate industry specialization during the 1980s. Using a sample of 686 four-digit SIC industries and 64 two-digit industry groups, this study finds that aggregate industry specialization declined very slightly at both the four-digit and two-digit level between 1981 and 1989. This study also finds that sell-offs of establishments through corporate control transactions or interfirm asset sales had no significant effect on aggregate industry specialization.