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Hindered amine light stabilizers (HALS) and UV absorbers (UVA) added to pigmented coatings adsorb on certain pigment and ultrafine oxide particles. Analysis of adsorption isotherms taken in xylene solutions and spectroscopic data revealed that chemisorption is the dominant interaction mechanism between the light stabilizers and the pigment particles. In contrast, the stabilizer interactions with ultrafine oxide particles are based on van der Waals forces, i.e., physical adsorption. In thermoset coatings, the chemisorbed stabilizers remain bound to the pigment surface on cure. The physically adsorbed stabilizers desorb on cure and migrate within the coatings. The chemistries involved in chemisorption were investigated using Fourier transform infrared spectroscopy and time-of-flight secondary ion mass spectroscopy. Stabilizers containing ester linkages hydrolyze to varying degrees into carboxy-late salts and alcohols. Acetyl groups also hydrolyze. Some of the chemisorbed light stabilizers lose the ability to protect coatings from photodegradation.

Adsorption experiments have been carried out to understand the interactions responsible for UV light stabilizer adsorption on pigments in coatings. Light stabilizer adsorption on various pigments was studied in xylene solutions to eliminate potential interference from the cure process. Adsorption isotherms were determined for UV absorbers and hindered amine light stabilizers (HALS) compounds. Infrared spectral analysis revealed that chemical interactions at the pigment surface are responsible for the observed effects. In some cases the chemical surface interactions are likely to prevent the adsorbed molecules from functioning as light stabilizers.

To understand the role of tendon fibroblast contraction in tendon healing, we investigated the contraction of human patellar tendon fibroblasts (HPTFs) and its regulation by transforming growth factor-beta1 (TGF-beta1), TGF-beta3, and prostaglandin E(2) (PGE(2)). HPTFs were found to wrinkle the underlying thin silicone membranes, demonstrating that these tendon fibroblasts are contractile. Using fibroblast populated collagen gels (FPCGs), exogenous addition of TGF-beta1 or TGF-beta3 was found to increase fibroblast contraction compared to non-treated fibroblasts in serum-free medium, whereas PGE(2) was found to decrease the tendon fibroblast contraction. Moreover, the tendon fibroblasts in collagen gels treated with TGF-beta1 contracted to a greater degree than those treated with TGF-beta3. Since the extent of fibroblast contraction is related to scar tissue formation, this differential effect of TGF-beta1 and TGF-beta3 on HPTF contraction supports the previous finding that TGF-beta1 induces scar tissue formation, whereas TGF-beta3 reduces its formation. Further, the reduced tendon fibroblast contraction by PGE(2) suggests that excessive presence of this inflammatory mediator in the wound site might retard tendon healing. Taken together, the results of this study suggest that regulation of human tendon fibroblast contraction may reduce scar tissue formation and therefore improve the mechanical properties of healing tendons.

To understand the role of tendon fibroblast contraction in tendon healing, we investigated the contraction of human patellar tendon fibroblasts (HPTFs) and its regulation by transforming growth factor-beta1 (TGF-beta1), TGF-beta3, and prostaglandin E(2) (PGE(2)). HPTFs were found to wrinkle the underlying thin silicone membranes, demonstrating that these tendon fibroblasts are contractile. Using fibroblast populated collagen gels (FPCGs), exogenous addition of TGF-beta1 or TGF-beta3 was found to increase fibroblast contraction compared to non-treated fibroblasts in serum-free medium, whereas PGE(2) was found to decrease the tendon fibroblast contraction. Moreover, the tendon fibroblasts in collagen gels treated with TGF-beta1 contracted to a greater degree than those treated with TGF-beta3. Since the extent of fibroblast contraction is related to scar tissue formation, this differential effect of TGF-beta1 and TGF-beta3 on HPTF contraction supports the previous finding that TGF-beta1 induces scar tissue formation, whereas TGF-beta3 reduces its formation. Further, the reduced tendon fibroblast contraction by PGE(2) suggests that excessive presence of this inflammatory mediator in the wound site might retard tendon healing. Taken together, the results of this study suggest that regulation of human tendon fibroblast contraction may reduce scar tissue formation and therefore improve the mechanical properties of healing tendons.

A cohort of 3-year survivors of head and neck cancer was evaluated for persistent quality of life (QOL) concerns and long-term treatment effects.Mailed questionnaire.The questionnaire with the University of Washington Quality of Life (UWQOL) scale, the Performance Status Scale for Head and Neck Cancer (PSS-HN), the Functional Assessment of Cancer Therapy (FACT) scale, and the Functional Assessment of Cancer Therapy Head and Neck (FACT-HN) scale and locally prepared questions was sent to 111 3-year disease-free survivors. Analysis was performed to statistically evaluate the effect of stage, site, treatment type, surgery, and cancer concern on QOL. Current smoking information was gathered.Seventy-two survivors completed the questionnaire. Advanced stage was correlated with lower QOL scores in the domains of disfigurement, chewing ability, speech, and eating in public. QOL scores did not vary by initial tumor site. Patients treated with irradiation alone had statistically better QOL scores than those treated with combined surgery/radiation therapy in the pain, disfigurement, chewing, and speech domains. Laryngectomy and composite resection survivors reported lower QOL scores than patients treated with irradiation alone. A low level of cancer concern persisted in about half of the long-term survivors. Cancer concern was associated with continued pain, disfigurement, and limitations on eating in public. Three-quarters of the tobacco users had quit by the time of the questionnaire. Nevertheless, the patients were not thoroughly convinced that tobacco had caused their cancer.Long-term survivors of head and neck cancer experience QOL effects well after completion of treatment. Effects are most pronounced in survivors who required combined surgery/radiation therapy. Continuing low levels of cancer concern persist in about half of the survivors. Many cancer survivors successfully quit smoking.

A functional neotongue following total glossectomy requires both soft-tissue bulk and reconstruction of muscle function. We used innervated transverse gracilis musculocutaneous flaps to reconstruct total glossectomy defects in eight patients. The obturator nerve to the gracilis muscle was approximated to the hypoglossal nerve to reinnervate the gracilis muscle by using microsurgical technique. The cutaneous paddle of the gracilis flap easily supplies sufficient bulk to replace the total glossectomy defect. Follow-up of patients ranged from 3 to 47 months. All patients were able to resume oral feeding. Electromyographic studies performed on one patient showed reinnervation of the flap with active elevation of the posterior pharynx. Ultimately, seven patients died because of recurrence of their disease. The innervated gracilis musculocutaneous flap may benefit patients who have a total glossectomy by allowing them to achieve a more functional recovery.

More than 90% of upper aerodigestive tract (UADT) cancers occur in people with specific lifestyle risks, including tobacco and alcohol use. More than 90% of tumors occur in easily examined parts of the head and neck, therefore, there is the possibility of identifying the vast majority of patients through selective screening. Physicians should keep in mind that the mucosa's sojourn from visually suspicious (and possibly malignant) tissue is most likely less than two years, and frequent examination of asymptomatic patients is necessary. When patients wait to bring symptoms to medical attention, their cancers will be advanced 60% of the time when the chance of cure is less than 30%. Given the difficulty of implementing regular examinations in a poorly compliant, high risk population, genetic and molecular screening tools may allow very high risk individuals to be identified.

Metastatic neck nodes in patients with squamous cell carcinoma of the head and neck are most commonly managed by surgery, radiotherapy, or combined-modality therapy. For combined-modality cases, the sequencing of surgery and radiotherapy is generally guided by which modality is considered preferable for treatment of the primary tumor. A postradiotherapy neck dissection is often considered for those patients withN1 disease in which the primary is treated with radiotherapy alone.Between February 1991 and October 1995, 25 patients with node-positive squamous cell carcinoma of the head and neck were treated with planned unilateral (n = 22) or bilateral (n = 3) neck dissection following high-dose radiotherapy. The primary tumor sites included: tongue base (n = 11), tonsil (n = 6), nasopharynx (n = 3), pyriform sinus (n = 2), supraglottic larynx, (n = 1), soft palate (n = 1), and unknown head and neck primary (n = 1). The specific nodal stage breakdown of the 28 individual neck dissections (25 patients) was N1 (n = 1), N2A (n = 5), N2B (n = 15), N3 (n = 7).Nineteen of the 28 neck dissections (68%) demonstrated no evidence of residual carcinoma. Of the nine positive neck dissections, six revealed malignant cells in a single nodal echelon. The 1- and 2-year rate of neck control in all 25 patients was 100% and 93%, respectively. The 1- and 2-year disease-specific survival for all 25 patients was 83% and 60%, respectively. With a minimum follow-up of 2 years, 64% of the 25 patients remain alive with no evidence of disease or dead of non-cancer causes.In this series of postradiotherapy neck dissections, two thirds of the dissections demonstrated no evidence of residual tumor (19/28, or 68%). However, there was not a direct correlation between pretreatment nodal size (neck staging), radiation dose delivered, and the likelihood of achieving a cancer-free neck dissection. Only one of 28 postradiotherapy neck dissections identified tumor outside of nodal stations II-IV. The predictable pattern of residual disease in pathologically positive cases suggests that a selective neck dissection encompassing levels II-IV may be appropriate in a majority of patients.

Tracheal stenosis can be a troubling consequence of laryngectomy. Some revision techniques disturb the posterior stoma site of a current or planned tracheoesophageal puncture (TEP).A revision technique which advances the trachea out of the stoma, divides the anterior tracheal wall, and leaves the posterior tracheal wall undisturbed was designed. The paper describes the technique in detail. "Success" was defined as producing a stable, trouble-free stoma requiring no stenting; "partial success" as an improved stoma requiring some stenting; and "failure" as no improvement and continuous stenting.Fifteen patients underwent the procedure. Median time from laryngectomy to revision was 10 months. Preoperative to postoperative median stoma size increased from 63 mm2 to 135 mm2. Seven patients were classified as successful, six patients were partially successful, and two patients had no improvement.The tracheal advancement flap is a safe technique for the laryngectomy patient who has undergone or might undergo voice restoration.

A rare case of mixed ependymoma and astrocytoma of the cerebellopontine angle is reported. Its clinical presentation, characteristics on evaluation, and prognosis are compared with those of the acoustic neuroma and glioma. The central form of von Recklinghausen's disease and familial multiple lipomatosis as it applies to the patient is also discussed.

A family of digital attitude reference systems (DARS) is developed for three-axis-stabilized, earth-oriented satellites. It includes the complete DARS configuration, which utilizes measurements from a sun sensor in addition to the horizon sensors and gyros in use on conventional analog gyrocompassing-type reference systems (CARS). The complete configuration also utilizes statistically optimal (Kalman) filtering to process these measurements to estimate and compensate for important measurement errors as well as to estimate the spacecraft attitude. Various suboptimal configurations of DARS are also studied. Based on simulation results, the attitude accuracies of the two most promising DARS configurations are approximately 0.03 and 0.04 deg, respectively, and the convergence time of both systems is less than 20 sec. Thus, DARS is shown to fill the important gap between low-accuracy gyrocompassing systems (using horizon sensors and gyros) and high-accuracy systems (requiring star sensors or trackers) by achieving intermediate attitude accuracy at the expense of low-to-medium complexity. (Author)