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Readmissions pose a significant hardship for patients and constitute a major quality and financial concern for hospitals. We sought to define risk factors associated with hospital readmission after colorectal surgery at a tertiary care hospital. We evaluated readmission among all patients who underwent a colorectal surgical procedure between July 16, 2007 and June 30, 2011. In a cohort of 4879 operative encounters, 492 (10%) were readmitted to the hospital within 30 days of discharge. Procedures with highest readmissions included stoma creation (22%), ileoanal pouch surgery (22%), and total proctocolectomy (30%). In multivariate analysis, the following variables were associated with risk of readmission: postoperative complication, use of anxiolytics, high comorbidity score, patient setting, alcohol use, and stoma creation. Surgeon of record was not associated with readmission. In conclusion, several patient, procedural, and postoperative factors were associated with an increased risk of readmission. Considerably high rates of readmission were noted after stoma creation, ileoanal pouch procedures, and proctocolectomy. Surgeon of record was not associated with risk of read-mission, indicating little value to this metric as a physician-specific indicator of quality.

Self-localization of an underwater vehicle is particularly challenging due to the absence of Global Positioning System (GPS) reception or features at known positions that could otherwise have been used for position computation. Thus Autonomous Underwater Vehicle (AUV) applications typically require the pre-deployment of a set of beacons. This thesis examines the scenario in which the members of a group of AUVs exchange navigation information with one another so as to improve their individual position estimates. We describe how the underwater environment poses unique challenges to vehicle navigation not encountered in other environments in which robots operate and how cooperation can improve the performance of self-localization. As intra-vehicle cornmunication is crucial to cooperation, we also address the constraints of the communication channel and the effect that these constraints have on the design of cooperation strategies. The classical approaches to underwater self-localization of a single vehicle, as well as more recently developed techniques are presented. We then examine how methods used for cooperating land-vehicles can be transferred to the underwater domain. An algorithm for distributed self-localization, which is designed to take the specific characteristics of the environment into account, is proposed. We also address how correlated position estimates of cooperating vehicles can lead to overconfidence in individual position estimates. Finally, key to any successful cooperative navigation strategy is the incorporation of the relative positioning between vehicles. The performance of localization algorithms with different geometries is analyzed and a distributed algorithm for the dynamic positioning of vehicles, which serve as dedicated navigation beacons for a fleet of AUVs, is proposed. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

The cavitation damage resistance of several fiber reinforced polymeric composite systems was evaluated before and after seawater immersion via a modified ASTM G-32 method utilizing a stationary specimen. For both dry and saturated condi tions, a carbon fiber/thermoplastic toughened epoxy matrix composite (IM7/977-2T) was found to perform the best under cavitation attack, while carbon fiber/thermoplastic matrix (AS4/PEEK) was found to be the least resistant. Glass/epoxy composites (E-Glass/5920, Scotch Ply 1002) were intermediate in erosion resistance. Moisture absorption was seen to decrease the erosion resistance of both E-Glass/5920 and AS4/APC-2 materials, while increasing the resistance of SP 1002; IM7/977-2T was not affected by immersion. All mate rials show decreasing erosion rates due to material recession from the cavitation cloud and increasing collapse-shielding with exposure time. A reduction in water hammer pressure was estimated by incorporating finite material impedance into the water hammer equation. Using simplifying assumptions, a 15 percent reduction in water hammer pressure is calculated.

Little, if any, information regarding the effects of seawater immersion on the impact resistance of composite materials has been published to date. In the present study, instrumented impact tests were used to characterize such effects for two glass fiber reinforced epoxy composites. One material consisted of continuous nonwoven E-glass fibers in a conventional epoxy resin and the other consisted of woven E-glass fibers in a rubber toughened epoxy resin formulated specifically for marine applications. In the conventional epoxy system, the energy for incipient damage increased significantly follow ing seawater immersion due to plasticization of the matrix by the absorbed moisture. Both glass/epoxy systems experienced substantial reductions in peak load and energy absorbed at peak load as a result of moisture-induced degradation of the fibers and fiber/matrix interface. Energy after peak load decreased in the conventional epoxy system follow ing immersion. Total energy absorbed was reduced significantly for both glass/epoxy systems following seawater immersion. These results indicate that moisture-induced degradation can significantly reduce the impact resistance of glass fiber reinforced epoxy composites.

Few comprehensive studies on the effects of stacking sequence and rein forcement form (unidirectional versus woven) have been published to date and much of the available data is contradictory. In the present study, instrumented impact tests were used to characterize such effects for carbon fiber reinforced thermoplastic toughened epoxy laminates. Impact resistance was characterized in terms of load and energy parameters measured during penetration tests. These parameters were related to damage in the lami nates by conducting rebound tests followed by ultrasonic imaging and microscopy. The results clearly demonstrated a relationship between the onset of damage and the first peak in the load versus deflection plots obtained in the penetration tests. No major effects of stacking sequence or reinforcement form were apparent in terms of the energy required for the onset of damage in the laminates. Energy to maximum load was found to be highly de pendent on stacking sequence. Substitution of woven reinforcement for unidirectional tape in a quasi-isotropic layup resulted in a substantial decrease in the energy to maximum load. The results in terms of peak load showed similar trends. No effects of stacking se quence or reinforcement form were observed in terms of energy after peak load. It is ap parent from this work that stacking sequence and reinforcement form can have significant effects on impact resistance particularly at higher impact energies.

Aluminum matrix composites with reinforcement of planar-random graphite fibers, SiC whiskers, or alumina particulates have been evaluated for their high temperature performance. The composites were aged at 150 and 200°C for up to 500 hours. Microhardness results indicate accelerated aging of the composites in comparison with that of wrought 6061 Al resolutionized and aged under identical conditions. The aging response of the composites depends on the characteristics of the reinforcements. The graphite fiber reinforced composites and the silicon carbide whisker reinforced compos ites retain their tensile strength and stiffness in the overaged condition of the matrix. The composites were tested for their tensile stiffness and strength at temperatures of 150 to 350°C. The Young's modulus of all the composites remain relatively constant up to 350°C. Both the graphite fiber and silicon carbide whisker reinforced composites show substantial strength advantage over that of the wrought 6061 Al at all temperatures. The silicon car bide whisker and alumina particulate composites were evaluated for their creep behavior. These composites were subjected to creep deformation at temperatures of 232 to 350°C under stresses of up to 100 MPa. The whisker reinforced composite shows significant re sistance to creep; about two orders of magnitude lower steady state creep rates than that of the wrought aluminum. The particulate composite had a moderate increase in creep resistance.

Laminated silicon carbide (SiC) whisker/alumina (Al2O3) composites were fabricated by tape casting and hot pressing. Whisker loadings of 10 and 20 vol % were produced with a predominance of fiber orientation in the direction of casting. Elastic, thermal and mechanical properties of the composites were measured in the longitudinal and transverse directions. The elastic moduli for 10 and 20 whisker vol% Al2O3 composites were approximately the same as unreinforced alumina. The coefficient of thermal expansion was reduced by the addition of the whiskers. The fracture toughness of the composites increased with whisker content from 3.8 MPa m1/2 for pure alumina to 8.0 MPa m1/2 for 20 vol% whiskers in the longitudinal direction.

A consecutive series of 35 clinically non-secretory pituitary adenomas treated surgically by the trans-ethmoidal approach is presented. Mean age at presentation was 60 years, with a male-to-female ratio of 2:1. These tumours present later than hormone secreting tumours: 90% were over 2 cm in diameter at operation. Seventy-one per cent of patients had impaired vision and 89% had hypopituitarism. Surgical treatment relieved or significantly improved visual fields in 79% of patients with impaired vision. Ninety-one per cent required permanent hormone replacement. Mean follow-up was for 4.4 years. Five tumours recurred, causing recurrent visual symptoms. No tumours recurred in those patients treated with postoperative radiotherapy, but follow-up in this group was only for a mean of 2.7 years.

Distributed algorithms often cannot be analyzed to give an accurate estimate of performance. ELECTOR, a program written in OCCAM™(a parallel pro gramming language) has been developed to simulate a class of distributed algo rithms, election algorithms. This simula tor and a description of the methods used to design a distributed system simulator are presented. A description of the design of an equivalent simulator on a SIMD machine (the Connection Machine) is then presented. Simulation results from ELECTOR for the performance of three election algorithms are presented. These results show that the performance of election algorithms with similar upper bounds on average number of messages transmitted can be better evaluated by simulation. Results from the second simulator for one of these algorithms confirm the validity of the first results.

A 63-year-old man presented in 1992 with left basal pneumonia and septicaemia. Protein electrophoresis revealed a dense discrete and abnormal band in the gamma region. His serum IgM concentration was grossly increased at 82·8 giL (reference range 0,42-2'6) and bone marrow biopsy revealed an increase in lymphoid cells, some of which showed plasma cell characteristics of binucleate forms consistent with Waldenstrom's macroglobulinaemia. He was treated with intermittent courses of chlorambucil and prednisolone with a satisfactory response, and his IgM fell to 20 g/L. His serum calcium adjusted for albumin was normal at 2·53 rnmol/L on presentation, but increased to 2·84mmol/L in August 1993 and then to 3·55 mrnol/L in December 1994 (Fig. 1). His serum parathormone (PTH) concentrations measured on three occasions when he was hypercalcaemic were within the reference range (Chi ron Magic LitePTH =2-4, 2·5 and 2·5 pmol/L; reference range 0'9-5-4) but were inappropriate for his degree of hypercalcaemia. He had normal thyroid function, and no evidence of sarcoidosis. His parathormone related peptide was below the limit of detection and his urinary calcium excretion was normal at 5·0 mmol/24 h. Radiological examination revealed osteoporosis of his

Several graphite fiber reinforced (planar random) metal matrix composites employing copper, aluminum, tin and babbitt matrices were fabricated by a newly devel oped high-pressure squeeze casting method. The fiber volume fraction of these composites ranged from 5 to 55%. These composites had relatively weak fiber-to-matrix bonding because of the near-absence of interfacial reaction between fiber and matrix materials. The tensile strength of these composites increased with fiber volume fraction up to about 25% followed by a gradual decrease for higher fiber volume fractions. Experiments were designed to evaluate various mechanical and physical properties of high pressure squeeze cast composites including the damping capacity and corrosion re sistance. Measurements of logarithmic decrement values at reasonant frequencies on can tilevered beam specimens have demonstrated that the damping capacity of the composites is much superior to that of wrought 6061-T6 Al and mechanically alloyed aluminum. Results on corrosion resistance of the composites in distilled water and 3.5% NaCl solu tion over a range of voltages and temperatures are presented and discussed.

Understanding the principles of transactional analysis will help you and your staff head off negative interactions- with each other and with customers

Early adolescent values profiles were examined in five schools using a modified form of the Values Preference Survey Scale (Form D). The schools were differentiated on four bases: ethnic mix/Caucasian, religiously affiliated/public, urban/rural, and low SES/upper middle SES. Values ranking from 266 students, 10 to 12 years old, confirm the expectation that values profiles or orders of arrangement do differ from school to school and that the differences are significantly related to distinctions between schools on a composite dimension that includes ethnicity, SES, and rural/urban factors. Somewhat fewer significant distinctions were found for religiously affiliated schools compared with public schools. Groups of upper middle SES, Caucasian children in non-urban communities assigned high values to achievement and recognition and balanced their appraisal with lesser weights for family and personal values. The urban, low SES, and mixed ethnic group developed a very different profile, assigning personal satisfactions priority above the values of reputation, achievement, religious faith, and secure country. The groups identified as Catholic ranked religious faith and personal virtues significantly high and prosperity relatively low.

The findings obtained from a survey of values among sixth grade pupils were compared with those of a survey from an earlier generation of pupils in 1972 using the same questionnaire in the same schools and at the same grade level. There was complete agreement on three of the highest values, all indicating a preference for love and affection. Differences in ranking across the decade were for mid-level items with the 1982 group elevating a few relatively individualistic values and reducing the rankings of more social values such as Politeness and A Secure Country. Comparisons were also made for sub-groups of the 1982 population by sex and ethnicity. The proportion of each sub-group that ranked an item above the mean for the generational group is reported. Only 8 out of 116 values were significantly different across groups, a finding consistent with evidence that agreement within a generational group tends to be strong.

High pressure squeeze casting has been developed to fabricate unidirec tional fiber reinforced metal matrix composites having a wide range of fiber volume frac tion. The process development required innovative die-design in order to minimize the direct contact of molten metal with the metallic die, to prevent liquid metal escape from the die, to ensure fast infiltration and rapid solidification under high pressure. However, the application of high pressure causes certain difficulties, such as maintaining all fibers aligned in one direction and ensuring their uniform distribution in any cross section of the composites. This paper addresses the techniques used to overcome these difficulties. Tensile test results for graphite fiber reinforced aluminum matrix composites are pre sented and discussed. Optical and scanning electron microscopy analysis of polished and fracture surfaces provide details of fiber/matrix interface characteristics and fracture mechanisms of the composites.

Explores the evolution of trade unions in Italy. Industrialization of the country; Role of workers in political unionism; Barriers to labor unity and growth; Economic changes in the country. (Abstract copyright EBSCO.)

How may teacher education go beyond the conventional channels in developing a deeper understanding of human rela tionships? Can enriching experiences be extended at the preservice level? How can the institution take fullest advantage of the resources in its area? These are some of the issues explored by Mr. Free hill, Director, Bureau of Research, West ern Washington College of Education, Bellingham.

During the 1950's, liberals and intellectuals, once keenly partisan to organized labor, began to voice acute criti cism of American unions. This change, superficially consid ered, seemed to savor of tergiversation. However, a review of the historical relationship of liberals and intellectuals to union ism revealed that the close and relatively long alliance of the 1930's and 1940's itself constituted a distinctive departure from prior American experience. Moreover, the historical approach indicated that the alliance limited itself almost entirely to CIO unions as agencies of reform and excluded nearly all unions of the AFL. As the two organizations came, in time, to resemble each other in their institutional lives, disenchantment set in. This development was inevitable since liberals and intellectuals have traditionally tended to view the functions of unions as more extensive and exalted than the destiny envisaged by unions for themselves. Today, then, liberals and intellectuals have resumed their historical relationship to American union ism by becoming once again the independent guardians of the public good for the community at large.

The development of a democratic, anti-Communist, and effective labor movement in Italy is rendered difficult by several things: the lack of po litical unity and a single economic ideology of the large national federations, the top-heavy administrative structure, and the well-rooted system of highly centralized control. Industry-wide bargaining has proved ineffective in getting the greatest benefits to labor in various sections of the country. Factory unions are being looked upon now as the answer; they have begun to be established but have not yet become effective instruments. What is needed is a new type of leadership which can build the labor movement from the bottom up rather than from the top down. Young labor leaders are now being trained, and in their hands lies the key to the future of the Italian labor movement.—Ed.