Biomedical subjects

A M Higgins

Publications and source records attributed to A M Higgins.

6 recordsLinked to original sources

PubMed2006

Early-stage roughening of the polymer-polymer interface approaching the glass transition temperature by real-time neutron reflection.

The early-stage roughening of the interface between thin deuterated poly(methyl methacrylate) (d-PMMA) layers on thick polystyrene (PS) films was studied as a function of the temperature using real-time specular neutron reflectivity. By measuring the growth of the interface roughness as a precursor of the dewetting, the characteristic time constant of the early stages of the process was studied as a function of the temperature approaching the glass transition temperature (T(g)) of the two polymers from above and compared with the prediction of the growth of the interface by the spinodal process. Both solid and liquid regimes were probed, in which the viscosity of the thin film or the substrate dominates respectively. The characteristic growth time of the process also depends on the upper film thickness to a power of 5 or 6 in the solid or liquid regimes, respectively, as predicted by the theory of spinodal dewetting.

Journal Article↗

PubMed2002

The timescale of spinodal dewetting at a polymer/polymer interface.

We investigate the dynamics of spinodal dewetting in liquid-liquid polymer systems. Dewetting of poly(methyl-methacrylate) (PMMA) thin films on polystyrene (PS) "substrates" is followed in situ using neutron reflectivity. By following the development of roughness at the PS/PMMA interface and the PMMA surface we extract characteristic growth times for the dewetting process. These characteristic growth times are measured as a function of the molecular weight of the two polymers. By also carrying out experiments in the regime where the dynamics are independent of the PS molecular weight, we are able to use dewetting to probe the scaling of the PMMA thin film viscosity with temperature and molecular weight. We find that this scaling reflects bulk behaviour. However, absolute values are low compared to bulk viscosities, which we suggest may be due in part to slippage at the polymer/polymer interface.

Journal Article↗

PubMed1996

Immunoblot analysis of anti-Ureaplasma urealyticum antibody in pregnant women and newborn infants.

The purpose of the present study was to determine the frequency in which antibody reactive to Ureaplasma urealyticum could be detected in a population of pregnant women and newborn infants. Serum samples from a prospective cohort of 80 healthy, U. urealyticum culture-positive and culture-negative pregnant women and a retrospective cohort of 522 infants born at between 25 and 42 weeks of gestation were studied by immunoblot analysis. Cultures of specimens from the lower genital tract were positive for U. urealyticum for 83% of the pregnant women, and serum immunoglobulin G (IgG) antibody which reacted to U. urealyticum was detectable in 93% of the pregnant women. Samples from five women (8%) had increases in the number of anti-U. urealyticum IgG bands over the course of the pregnancy. Samples from four of these five women had corresponding increases in the number of antibody bands present in IgA immunoblots. Six of the 522 samples from newborns or cord blood (1.1%) were positive for anti-U. urealyticum IgA; 5 of these 6 samples were also positive for IgM. The six anti-U. urealyticum IgA-positive infants were distributed as follows; 3 of 67 (4.5%) infants were delivered at 25 to 30 weeks of gestation, 3 of 176 (1.7%) infants were delivered at 31 to 34 weeks of gestation, and 0 of 279 infants were delivered at > or = 35 weeks of gestation. An antibody response to U. urealyticum can be detected in pregnant women and preterm infants and may serve as a marker of infection.

Adolescent↗

PubMed1993

Pharyngitis associated with herpes simplex virus in college students.

During a 16-month period patients who presented to the Syracuse University Health Center with upper respiratory complaints had throat swabs obtained for viral, streptococcal and Mycoplasma pneumoniae cultures. Thirty-five of 613 patients (5.7%) had herpes simplex virus (HSV) isolated. All but 2 of the HSV isolates were found to be type 1 by immunofluorescent staining. Two HSV-positive patients also grew Group A Streptococcus, one grew M. pneumoniae and three had serum heterophile antibody tests that were positive. On physical examination 25 of the 35 HSV-positive patients had pharyngeal erythema and 14 had pharyngeal exudate. Twelve of these patients had vesicular lesions of the lips, throat or gums associated with their other symptoms. For 29 of the 35 HSV-positive students the primary diagnosis assigned was pharyngitis, for 2 the diagnosis was stomatitis and the remainder were assigned a primary diagnosis of upper respiratory infection, pneumonia, bronchitis or dental infection. Thirty-two of the 35 HSV-positive patients were treated with oral antibiotics and 7 were treated with oral or topical acyclovir. During the same 16-month period 89 (6.9%) of 1297 students presenting with sore throat were culture-positive for influenza A or B, 30 (2.3%) of 1283 were culture-positive for M. pneumoniae and 169 (2.8%) of the 6016 cultured for Group A Streptococcus were positive. Serum was tested for heterophile antibody in 2438 students, and 257 (10.5%) were positive. Herpes simplex virus is associated with pharyngeal symptoms in college students, and herpes simplex pharyngitis cannot easily be distinguished clinically from other causes of acute pharyngitis in this age group.

Acute Disease↗

PubMed1993

Rhinovirus infection associated with serious illness among pediatric patients.

Rhinovirus is an important cause of respiratory infection among all age groups, but it is primarily thought of as being responsible for upper respiratory tract infection. Rhinovirus was isolated from the respiratory tract of 48 pediatric patients who were hospitalized (40) or seen in a pediatric emergency room (8) during the period of July, 1985, through December, 1988. Twenty-eight (58%) of the patients presented during the spring and early summer. Forty-one (86%) of the 48 patients were less than 12 months of age. All except four of the patients had viral cultures performed because of respiratory symptoms. Bronchiolitis was the single most frequent clinical diagnosis and was noted in equal proportion among children less than 3 months and 3 to 12 months of age. Nine patients were assigned a diagnosis of suspected sepsis. Rhinovirus infection was a complication of underlying illness for 17 (44%) of the 40 hospitalized patients, and those patients tended to be older than the otherwise healthy hospitalized infants with rhinovirus. Twenty-six patients (54%) were treated with antibacterial agents, although only one patient was documented to have a concomitant bacterial infection (Chlamydia trachomatis). Overall rhinovirus isolation during the study period represented 0.7% of all specimens submitted for viral isolation compared with 8.2% for respiratory syncytial virus. Rhinovirus infection leads to hospitalization less frequently than does respiratory syncytial virus infection, but the severity of illness and clinical presentation in young infants are similar.

Adolescent↗

PubMed1991

Efficient fabrication of precise electron cut-outs.

A time-saving method for creating accurate patient-personalized cerrobend cut-outs, utilized in electron beam therapy, is described--implemented by radiographic films taken during simulation. This technique is used frequently (but not exclusively) for the treatment of head and neck cancer, where isocentric lateral films taken for photon treatment also provide the information needed to define the posterior off-cord electron boost. The boost field is traced from the film and demagnified by xerox to the distance of the cone cut-out holder. A second simulation of the electron field is not necessary. Matching of the electron fields to the photon fields is accurate, consistent, and easy to define on the patient.

Electrons↗