Showing papers by "University of Akron published in 1996"

Nanometre diameter fibres of polymer, produced by electrospinning

Abstract: Electrospinning uses electrical forces to produce polymer fibres with nanometre-scale diameters. Electrospinning occurs when the electrical forces at the surface of a polymer solution or melt overcome the surface tension and cause an electrically charged jet to be ejected. When the jet dries or solidifies, an electrically charged fibre remains. This charged fibre can be directed or accelerated by electrical forces and then collected in sheets or other useful geometrical forms. More than 20 polymers, including polyethylene oxide, nylon, polyimide, DNA, polyaramid, and polyaniline, have been electrospun in our laboratory. Most were spun from solution, although spinning from the melt in vacuum and air was also demonstrated. Electrospinning from polymer melts in a vacuum is advantageous because higher fields and higher temperatures can be used than in air.

Teachers’ Professional Community in Restructuring Schools

Abstract: Professional community among teachers, the subject of a number of recent major studies, is regarded as an ingredient that may contribute to the improvement of schools. The research reported in this article is grounded in the assumption that how teachers interact with each other outside of their classrooms may be critical to the effects of restructuring on students. The analysis focuses on the type of professional community that occurs within a school and investigates both the organizational factors that facilitate its development and its consequences for teachers’ sense of responsibility for student learning. The findings suggest that wide variation in professional community exists between schools, much of which is attributable to both structural features and human resources characteristics, as well as school level. Implications for current school reform efforts are discussed.

Corporate returns and cash conversion cycles

Abstract: This study examines the relationship between profitability measures and management of ongoing liquidity needs for a large cross-section of firms over a twenty-year period. Long-run equilibrium relationships between the cash conversion cycle, a measure of ongoing liquidity management, and alternative measures of profitability are tested using both nonparametric and multiple regression analysis. Industry and size differences are controlled. While there are exceptions to the general finding for specific firms and for specific industries, the paper offers strong evidence that aggressive working-capital policies enhance profitability.

Torque ripple minimization in switched reluctance motor drives by PWM current control

Abstract: Higher torque ripple is one of the few drawbacks of switched reluctance motor (SRM) drives which otherwise possess excellent characteristics for applications in many commercial drives. This paper begins with an extensive review of torque ripple reduction methods that appear in the literature and then presents a new strategy of PWM current control for smooth operation of the drive. This method includes a current control strategy during commutation when torque ripple minimization is of utmost importance.

Adhesion and Strength of Viscoelastic Solids. Is There a Relationship between Adhesion and Bulk Properties

Abstract: Strength of adhesion depends upon the rheology of an adhesive as well as upon its interaction with a substrate. This is shown by studies using model joints prepared with different amounts of interlinking between two rubber sheets. The fracture energy G per unit of interfacial area appears to be a product of two terms: G = Go [1 + f(R,T)], where Go is the intrinsic (chemical) strength of the interface and f(R,T), usually much larger than unity, reflects energy dissipated viscoelastically within the adherends at a crack speed R and temperature T. Values of Go range from virtually zero for nonbonded sheets up to the threshold tear strength of rubber, 50−80 J/m2, in proportion to the density of interfacial bonds. Values of G are as much as 1000× greater at high speeds and low temperatures. Like adhesion, the tear strength of a soft rubbery solid is also increased by internal energy losses and shows the same marked dependence upon rate of tearing. By comparing the rate R at which tear strength increases by a ...

Angiotensin-(1-7) Inhibits Vascular Smooth Muscle Cell Growth

Abstract: Although angiotensin II (Ang II) and the heptapeptide Ang-(1-7) differ by only one amino acid, the two peptides produce different responses in vascular smooth muscle cells. We previously showed that Ang II stimulated phosphoinositide hydrolysis, whereas Ang II and Ang-(1-7) released prostaglandins. We now report that Ang II and Ang-(1-7) differentially modulate rat aortic vascular smooth muscle cell growth. Ang-(1-7) inhibited [3H]thymidine incorporation in response to stimulation by fetal bovine serum, platelet-derived growth factor, or Ang II. The reduction in serum-stimulated thymidine incorporation by Ang-(1-7) depended on the concentration of the heptapeptide over the range of 1 nmol/L to 1 mumol/L, with a maximal inhibition of 60% by 1 mumol/L Ang-(1-7). Ang-(1-7) also inhibited the serum-stimulated increase in cell number to a maximum of 77% by 1 mumol/L Ang-(1-7). The attenuation of serum-stimulated thymidine incorporation by Ang-(1-7) was unaffected by antagonists selective for angiotensin type 1 (AT1) or type 2 (AT2) receptors; however, [Sar1,Ile1]Ang II and [Sar1,Thr2]Ang II were effective antagonists, indicating that growth inhibition by Ang-(1-7) was a result of angiotensin receptor activation. In contrast, Ang II stimulated [3H]thymidine incorporation in cultured vascular smooth muscle cells over the same concentration range, with a maximal stimulation of 314% at 1 mumol/L Ang II. Ang II also increased the total number of cells (to 145% of control), suggesting that enhanced thymidine incorporation was associated with vascular smooth muscle cell proliferation. The AT1 antagonist losartan or L-158,809 but not AT2 antagonists blocked [3H]thymidine incorporation by Ang II. These results suggest that Ang-(1-7) and Ang II exhibit opposite effects on the regulation of vascular smooth muscle cell growth. The inhibition of proliferation by Ang-(1-7) appears to be mediated by a novel angiotensin receptor that is not inhibited by AT1 or AT2 receptor antagonists.

Li+, Na+, and K+ Binding to the DNA and RNA Nucleobases. Bond Energies and Attachment Sites from the Dissociation of Metal Ion-Bound Heterodimers

Abstract: The alkali metal ion (M+ = Li+, Na+, K+) affinities of the common DNA and RNA nucleobases are determined in the gas phase by investigating the dissociation of metal ion-bound heterodimers [nucleobase + B]M+, in which B represents a reference base of known affinity (kinetic method). The dimer ion decompositions are assessed at two different internal energies, namely from metastable precursor ions and after collisional activation. This approach makes it possible to deconvolute entropy from enthalpy and, therefore, leads to more accurate affinity (i.e. enthalpy or bond energy) values. For the nucleobases studied, viz. guanine, cytosine, adenine, thymine, and uracil, the corresponding M+−nucleobase bond energies are (kJ mol-1) as follows: 239, 232, 226, 215, and 211 with Li+; 182, 177, 172, 144, and 141 with Na+; and 117, 110, 106, 102, and 101 with K+. The method used also provides quantitative information about the overall entropy change occurring upon the dissociation of the heterodimers; this change is m...

Patterns of dissociation in clinical and nonclinical samples.

Abstract: Research has consistently found elevated mean dissociation scores in particular diagnostic groups. In this study, we explored whether mean dissociation scores for different diagnostic groups resulted from uniform distributions of scores within the group or were a function of the proportion of highly dissociative patients that the diagnostic group contained. A total of 1566 subjects who were psychiatric patients, neurological patients, normal adolescents, or normal adult subjects completed the Dissociative Experience Scale (DES). An analysis of the percentage of subjects with high DES scores in each diagnostic group indicated that the diagnostic group's mean DES scores were a function of the proportion of subjects within the group who were high dissociators. The results contradict a continuum model of dissociation but are consistent with the existence of distinct dissociative types.

Argumentativeness and Verbal Aggressiveness: A Review of Recent Theory and Research

Abstract: A good deal of research on argumentativeness and verbal aggressiveness has been conducted in the communication discipline in this and the previous decade. The research has been based on a personali...

Resection arthrodesis of the knee with an intercalary allograft.

Abstract: Thirty-nine patients who had a malignant or an aggressive benign bone tumor about the knee were managed with a resection arthrodesis with use of an intercalary allograft fixed with an intramedullary nail. In thirty-one patients, this was the method chosen for the initial reconstruction after resection of the tumor. In eight patients, another type of reconstruction had already failed. Both the proximal and the distal allograft-host junction healed and the functional outcome was satisfactory in thirty-two patients. Non-union developed in seven patients: at one junction in six patients and at both junctions in one. In five patients, the non-union healed after bone-grafting, repeat internal fixation, or replacement of the allograft. An above-the-knee amputation was done for two patients, both of whom had had a chronic non-union. One patient had a local recurrence, and it was treated with an above-the-knee amputation.

Cellular communication system with dynamically modified data transmission parameters

Abstract: An apparatus and process for improving the performance of a cellular communication system using direct sequence spread spectrum techniques. The apparatus and process enable dynamic modification of communication system parameters including PN code length, chipping rate and modulation technique for transmission of a data packet. Modification is based on proximity of the transmitter and receiver, transmitter and receiver capabilities, and other factors. The system evaluates tradeoffs between data transmission speed and communication range to improve system performance.

Assessing Perceptions of Career-Related Barriers: The Career Barriers Inventory:

Abstract: The number and type of barriers that one perceives can be a limiting factor in career choice and implementation, and the construct of perceived career barriers has been increasingly recognized as a...

Nitric Oxide-Releasing Polymers Containing the (N(O)NO) - Group

Abstract: Ions of structure X[N(O)NO]- display broad-spectrum pharmacological activity that correlates with the rate and extent of their spontaneous, first-order decomposition to nitric oxide when dissolved. We report incorporation of this functional group into polymeric matrices that can be used for altering the time course of nitric oxide release and/or targeting it to tissues with which the polymers are in physical contact. Structural types prepared include those in which the [N(O)NO]- group is attached to heteroatoms in low molecular weight species that are noncovalently distributed throughout the polymeric matrix, in groupings pendant to the polymer backbone, and in the polymer backbone itself. They range in physical form from films that can be coated onto other surfaces to microspheres, gels, powders, and moldable resins. Chemiluminescence measurements confirm that polymers to which the [N(O)NO]- group is attached can serve as localized sources of nitric oxide, with one prototype providing sustained NO releas...

Portable telephone with integrated heads-up display and data terminal functions

Abstract: A portable telephone device with telephone, data terminal and/or heads-up display functions in an integrated package having a size and weight on the order of conventional portable wireless telephones. The device includes a hand-held body structure having a main body portion and a heads-up display body portion. The main body portion may be held in a normal telephone handset position at a side of a user's head to position audio input and output transducers in functional relationship to the user's mouth and adjacent ear. The heads-up display body portion is rotatable from a storage position to an operative position for locating a display in front of the adjacent eye of the user for display of data. The device further comprises, within the hand-held body structure, a processor and associated memory, a keyboard, a transceiver for voice and data communications with a remote telephone and/or data terminal unit, and a battery compartment for housing a battery that supplies power to the device.

Does job-related training performance decline with age?

Abstract: The meta-analytic review presents the findings of a project investigating the relationship between age and job-related training outcomes. The analysis is based on 83 effect sizes derived from 6,610 individuals. Results showed poorer training performance for older adults. In general, older adults, relative to younger adults, showed less mastery of training material (r = -.26), completed the final training task more slowly (r = .28), and took longer to complete the training program (r = .42). Field samples generally showed smaller age effects than laboratory samples. Estimated training performance for average individuals at various ages is provided.

Photoresponsive Monolayers Containing In-Chain Azobenzene

Abstract: Azobenzene monolayers on silicon have been prepared by two synthetic methods: (1) chemisorption of triethoxysilanes, and (2) acylation of amine-functionalized self-assembled monolayers with acid chloride derivatives. A series of films were prepared with different methylene spacer lengths and different terminal end groups (pentyl vs hydrogen). The resulting films were characterized using water contact angles, X-ray photoelectron spectroscopy, attenuated total reflectance infrared spectroscopy, and X-ray reflectivity (XR). Despite evidence for successful attachment of azobenzene to the surfaces, film thicknesses as determined by XR suggest uniform, but incomplete, monolayers. Irradiation of the films with 354 nm light effected a decrease in the water contact angle. The largest photoinduced changes in contact angles (9°) were observed for films prepared by acylation and with terminal pentyl groups; for one of these films, XR monitoring of film thicknesses showed a 1 A increase in film thickness during 354 n...

Recognizing dataforms in image areas

Abstract: Dataforms, such as bar codes and matrix codes, are recognized by analysis of histogram type data derived for a plurality of window sections of an image area. Typically, an image area 512 pixels high by 480 pixels wide is divided into 240 window areas, each including 1024 pixels in a 32 by 32 pixel square. A histogram for a window section overlying a portion of the dataform may typically exhibit two peaks representing the two principal reflective values (black and white, for example) of the elements and spaces of a dataform. A background (quiet zone) window section histogram exhibits one principal peak representing the background value (white, for example). The background window sections and the dataform window sections are assigned to two different groups. One or both groups are then used for one or more of the following: recognizing the presence of a dataform; determining whether the dataform is darker or lighter than the background; and locating the dataform within the image area. Also, a single histogram is used to identify the type of dataform, based upon the histogram signature of the dataform.

Head mounted communication system for providing interactive visual communications with a remote system

Abstract: A head mounted communication system provides interactive visual and audio communications between a user of the head mounted system and an operator of a remote system. The head mounted system includes a camera to pick up an image within the user's field of view. A display and optics are provided for projecting an enlarged image of displayed information at a distance from the user so as to be superimposed on the user's view of the real world. The system also includes a transmitter and receiver for providing two-way wireless communication between the head mounted system and the remote system so as to allow the operator of the remote system to see what the user of the head mounted system is viewing and to allow the user of the head mounted system to view via the display and optics video inputs received from the remote system so that they appear to be superimposed upon the real world.

A Kinetic-Model for Sulfur Accelerated Vulcanization of a Natural-Rubber Compound

Abstract: Vulcanization kinetics for a natural rubber compound were studied by a kinetic approach using the cure meter and DSC methods. A simplified but realistic model reaction scheme was used to simulate induction, curing, and overcure periods continuously. Physically significant parameters of the model were extracted from isothermal experimental data using a cure meter. The calculation demonstrated a good correspondence with isothermal cure meter data over the temperature range studied. The length of induction time, variation of maximum modulus with temperature, and the reversion phenomena observed from cure curves can be predicted. DSC data were found to be incompatible with the cure meter test, because the complex vulcanization reaction system is multiexothermal and it is difficult to isolate the heat due to crosslinking. Hence, the cure meter technique is suggested for the study of crosslink formation. The kinetic approach provides a way to incorporate vulcanization kinetics into simulation of reactive processing operations. © 1996 John Wiley & Sons, Inc.

Conservative Explicit Unrestricted-Time-Step Multidimensional Constancy-Preserving Advection Schemes

Abstract: The multidimensional advection schemes described in this study are based on a strictly conservative flux-based control-volume formulation. They use an explicit forward-in-time update over a single time step, but there are no “stability” restrictions on the time step. Genuinely multidimensional forward-in-time advection schemes require an estimate of transverse contributions to each face-normal flux for stability. Traditional operator-splitting techniques based on sequential one-dimensional updates introduce such transverse cross-coupling automatically; however, they have serious shortcomings. For example, conservative-form operator splitting is indeed globally conservative but introduces a serious “splitting error”; in particular, a constant is not preserved in general solenoidal velocity fields. By contrast, advective-form operator splitting is constancy preserving but not conservative. However, by using advective-form estimates for the transverse contributions together with an overall conservat...

Method for returning inbound calls

Abstract: Caller information is automatically taken from a caller on hold, the call disconnected and the call returned at the time when the caller would have been serviced had the caller stayed on hold. The caller's number is verified and either DTMF or verbal extension information is used to reconnect the call.

Emergency mobile routing protocol

Abstract: An emergency routing protocol within a wireless communication network. A mobile device can establish a communication link to the system backbone even when, for whatever reason, it can no longer communicate directly with a base station. The emergency routing protocol enables a distressed mobile device to communicate with the system backbone through another mobile device serving as an intermediary. The intermediary mobile device forwards information destined to/received from the distressed mobile device to its intended destination.

Dimensions of Masculinity: Relations to Date Rape Supportive Attitudes and Sexual Aggression in Dating Situations

Abstract: Sexual assault in general and date rape in particular are major issues for practitioners, educators, and researchers in counseling. This study sought to extend and refine existing research on the links between masculine gender roles and date rape by exploring 3 masculinity-related constructs that, until recently, have received relatively little attention in the context of rape research: masculinity ideology, attitudes toward feminism, and homophobia. In general, combinations of masculinity-related constructs were found to predict self-reported acceptance or perpetration of sexually coercive behaviors. Specifically, multiple regression analyses revealed that attitudes toward feminism and various, specific dimensions of masculinity ideology (vs. a global assessment, as in previous research) predicted unique variance in several types of date rape-supportive attitudes and beliefs: the Facade/Counterdependence dimension of masculinity ideology also predicted unique variance in self-reported history of sexual coercion. Implications for prevention, education, and future research are discussed.

Enhancement of wound repair with a topically applied nitric oxide-releasing polymer

Abstract: Nitric oxide is an important cytotoxic agent for host defense which also regulates gene expression, signal transduction, and vasodilation. In normal wounds, nitric oxide synthesis and metabolism are significantly increased during inflammation and tissue remodeling. However, nitric oxide production is suppressed in wounds where healing is impaired by diabetes or steroid-treatment. Topical delivery of nitric oxide in therapeutic amounts may alleviate this deficiency and thereby enhance wound repair. Consequently, we developed polyethyleneimine cellulose NONOate polymer, a nonsoluble, nontoxic, polymer-based NONOate--one of a new class of compounds that spontaneously release nitric oxide in a controlled fashion in aqueous media. Polyethyleneimine cellulose NONOate polymer was synthesized from polyethyleneimine cellulose to provide extended nitric oxide release with a half-life of 16 hours. Polyethyleneimine cellulose NONOate polymer or a control polymer was applied topically on full-thickness dermal wounds of rats at the time of wounding and days 3, 7, 10, 14, 17, and 21. Nitric oxide delivery was determined indirectly by measuring urinary nitrate. The first two polyethyleneimine cellulose NONOate polymer applications increased urinary nitrate output twofold to fourfold, whereas urinary nitrate output of control rats did not significantly increase. Nitrate output in polyethyleneimine cellulose NONOate polymer-treated rats was elevated compared with controls after each application, although this was attenuated in later applications. Rate of wound closure was measured with computer-based video imaging. Polyethyleneimine cellulose NONOate polymer-treated wounds were significantly smaller (p < 0.05) on days 7, 10, and 17 relative to controls, based on percentage of wound open relative to initial wound area. In a second experiment, telemetry-implanted rats were wounded to detect potential hypotensive effects as a result of polyethyleneimine cellulose NONOate polymer application. Topical polyethyleneimine cellulose NONOate polymer application to wounds showed no prolonged hypotensive effects, in contrast to a soluble NONOate which suppressed systolic blood pressure for over 6 hours. These results show that a nonsoluble, polymeric NONOate can provide topical nitric oxide delivery to wounds in a controlled manner, which may enhance wound healing. Further studies are in progress with other promising NONOate candidates to establish dose-response effects and therapeutic limits of exogenous nitric oxide release in impaired wound models.

Devulcanization of Waste Tire Rubber by Powerful Ultrasound

Abstract: Ground rubber tire (GRT) is devulcanized in a continuous process where the rubber crumb is conveyed by a screw extruder to a thin gap between a stationary die and a vibrating horn. Ultrasound amplitude, gap thickness and the duration of the treatment are varied, and their effect on the rubber properties is studied. The degree of devulcanization is characterized by the crosslink density and gel fraction of the devulcanized rubber. These characteristics are found to correlate uniquely with each other over a wide range of the treatment conditions. The results specific energy of ultrasound consumed per unit mass of the rubber is found to be the operating parameter correlating with the properties of the devulcanized rubber. The mechanical properties of thr re-vulcanized samples reach a maximum with an increasing degree of devulcanization, and then drop as a result of excessive degradation. Even without optimization of cure recipes, tensile strength and ultimate elongation of re-vulcanized tire rubber as high as 10.5 MPa and 250u, respectively, are achieved

Dynamically vulcanized thermoplastic elastomers

Abstract: Thermoplastic elastomers (TPEs) exhibit the functional properties of conventional thermoset rubber, yet can be processed on thermoplastic fabrication equipment. The great majority of TPEs ...