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Biomedical subjects

C Clay

Publications and source records attributed to C Clay.

At least 19 recordsLinked to original sources
PubMed2006

Water desorption from an oxygen covered Pt(111) surface: multichannel desorption.

Mixed OH/H2O structures, formed by the reaction of O and water on Pt(111), decompose near 200 K as water desorbs. With an apparent activation barrier that varies between 0.42 and 0.86 eV depending on the composition, coverage, and heating rate of the film, water desorption does not follow a simple kinetic form. The adsorbate is stabilized by the formation of a complete hydrogen bonding network between equivalent amounts of OH and H2O, island edges, and defects in the structure enhancing the decomposition rate. Monte Carlo simulations of water desorption were made using a model potential fitted to first-principles calculations. We find that desorption occurs via several distinct pathways, including direct or proton-transfer mediated desorption and OH recombination. Hence, no single rate determining step has been found. Desorption occurs preferentially from low coordination defect or edge sites, leading to complex kinetics which are sensitive to both the temperature, composition, and history of the sample.

Journal Article↗
PubMed2005

The structure of the mixed OH + H2O overlayer on Pt[111].

The structure of the mixed p(3 x 3)-(3OH + 3H2O) phase on Pt[111] has been investigated by low-energy electron diffraction-IV structure analysis. The OH + H2O overlayer consists of hexagonal rings of coplanar oxygen atoms interlinked by hydrogen bonds. Lateral shifts of the O atoms away from atop sites result in different O-O separations and hexagons with only large separations (2.81 and 3.02 angstroms) linked by hexagons with alternating separations of 2.49 and 2.813.02 angstroms. This unusual pattern is consistent with a hydrogen-bonded network in which water is adsorbed in cyclic rings separated by OH in a p(3 x 3) structure. The top-most two layers of the Pt atoms relax inwards with respect to the clean surface and both show vertical buckling of up to 0.06 angstroms. In addition, significant shifts away from the lateral bulk positions have been found for the second layer of Pt atoms.

Journal Article↗
PubMed2004

Hydrogen bonding in mixed OH+H2O overlayers on Pt(111).

The stability of OH on Pt(111) has been investigated to determine the role of hydrogen bonding in stabilizing the overlayer. We find that the optimal structure is a mixed (OH+H2O) phase, confirming recent density-functional theory predictions. The reaction O+3H(2)O forms a hexagonal (sqrt[3]xsqrt[3])R30 degrees -(OH+H2O) lattice with a weak (3x3) superstructure, caused by ordering of the hydrogen bonds. The mixed overlayer can accommodate a range of H(2)O/OH compositions but becomes less stable as the H2O content is reduced, causing defects in the hydrogen-bonding network that lift the (3 x 3) superstructure and destabilize the overlayer.

Journal Article↗
PubMed2001

[Corneal crystalline deposits in monoclonal gammapathy: a report of two cases].

Corneal immunoglobulin deposits are an unusual complication of lymphoproliferative affections such as monoclonal gammapathy of indeterminate significance, essential cryoglobulinemia, or multiple myeloma. Although uncommon, this crystalline keratopathy may be the first clinical sign of these malignant disorders. We report two cases of paraproteinic crystalline keratopathy: the first case is associated with a multiple myeloma, combined with cryoglobulinemia, and the second case with monoclonal gammapathy of indeterminate significance. In both cases, corneal crystalline deposits appeared before general clinical symptoms. In the first case, the systemic therapy made no change in the biomicroscopic aspect of the corneal deposit, despite immunoglobulin level normalization in the serum. Conversely, in the second case, we noticed a substantial regression of the corneal crystalline deposits as the systemic normalization. A review of the literature clarified the variety of clinical dorms of paraproteinic crystalline keratopathy, the physiopathogenics hypotheses that are currently being discussed, and the possible therapeutic modalities.

Aged↗
PubMed1998

Making sense of schizophrenic symptoms; delusional statements and behavior may be functional in purpose.

The present paper describes the use of a functional analysis in attempting to make sense of symptomatic delusional statements and behaviors that people diagnosed with schizophrenia present. The three categories that are used to classify symptoms are: (1) positive reinforcement function, (2) negative reinforcement function, and (3) mislabeling of private events. The paper presents a number of clinical cases whose symptoms are representative of each category. Each case is then functionally treated as a result of its "category" characteristics, thus basing treatment on the hypothesized function (or reason) for the symptom.

Adult↗
PubMed1996

Effects of AIDS counseling and risk reduction training on the chronic mentally ill.

The chronic mentally ill are a high-risk group for HIV infection. In this study 27 chronic mentally ill psychiatric outpatients were randomly assigned to either an AIDS education and risk reduction training group or to a no-treatment control group. Training was conducted during four 2-hour group meetings that were scheduled over 4 days. Treated patients were instructed on modes of HIV transmission and high-risk groups and practices. They were instructed on the importance of using condoms and also taught problem-solving and refusal skills to cope with high-risk sexual and drug and alcohol situations. Assessments were made immediately before and after training as well as during a 2-week follow-up. Participants who received training showed significant improvement in their knowledge about AIDS, their confidence to deal with high-risk situations, and on behavioral measures of coping in high-risk situations. No such improvement was noted in the control group. There was also evidence of maintenance over the 2-week follow-up. Although the magnitude of change was small, the results of the study are encouraging considering the brevity of treatment, the high degree of risk and difficulty faced with this patient population, and the fact that even a small amount of behavior change can make the difference between encountering and avoiding the HIV virus.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Superolateral approach to orbital tumors.

The conventional lateral approach to the orbit (Krönlein) does not allow a satisfactory view of the superior part of the orbit and the operative field is rather narrow. Therefore, large tumors which have developed not only laterally but also superiorly are usually approached transcranially. The craniotomy and exposure of the dura may be avoided when the tumor does not extend too far posteriorly and medially, by turning a larger orbital bone flap than the Krönlein's one. This technique was described by Nakamura as "type I orbitotomy" and can be referred to as a superolateral approach. After a bicoronal skin incision, a free orbital bone flap is cut. It includes the lateral orbital rim, a large external part of the superior orbital rim, and the lateral orbital wall. From 1985 to 1990 this approach was performed on 23 patients presenting with lacrimal gland tumors in 14 cases (11 pleomorphic adenomas, 2 adenoid cystic carcinomas, 1 adenocarcinoma), schwannomas in 2 cases, dermoid cyst in 1 case, hydatic cyst in 1 case, cavernous hemangiomas in 2 cases, inflammatory pseudotumor in 1 case, and mucoceles in 2 cases. This superolateral approach provides a wider exposure to the superolateral orbit than the classical Krönlein's approach and avoids the drawbacks of a craniotomy. A direct incision through the eyebrow can be used for bald people or for patients in poor condition.

Follow-Up Studies↗
PubMed1993

[Cavernous hemangioma of the orbit].

Cavernous hemangioma is one of the commonest primary orbital tumors. Painless and progressive reducible unilateral proptosis causing a variable degree of hyperopia is the usual clinical presentation. The case of a 39-year-old-female patient is reported. The clinical presentation was unilateral left axial proptosis with acquired hyperopia. Imaging studies showed a well circumscribed mass in the orbit, a superior neuro-surgical approach allowed complete resection of the tumor, and histopathology revealed the diagnosis of cavernous hemangioma.

Adult↗
PubMed1991

Tolerance of extended (28 day) continuous infusion of 5-fluorouracil in advanced head and neck cancer.

Since continuous exposure increases the cytotoxicity of 5-Fluorouracil, this agent is now commonly administered by 4-5 day continuous infusions. However Phase I studies have suggested that infusion of doses up to 450 mg/m2/day for at least 28 days may be possible. In the present study 12 patients with advanced head and neck cancer were treated with continuous infusion 5-Fluorouracil at starting doses of 400-450 mg/m2/day for 28 days followed by a 14 day rest period. Patients received a median of 2.5 cycles over 10 weeks for a median total 5-Fluorouracil dose of 12,700 mg/m2. One patient achieved Partial Response. Significant stomatitis (Grade II or greater) was seen more frequently than predicted from Phase I studies (8/12 patients) and was the most common cause for dose reduction. Diarrhea, emesis, palmar/plantar syndrome and skin rash were also noted. No significant myelosuppression was seen. Extremely large amounts of 5-Fluorouracil can be delivered to head and neck cancer patients by extended infusion. However due to the high frequency of stomatitis in this population, lower starting doses than those used in this study may be required.

Adult↗
PubMed1988

Heparin sodium versus 0.9% sodium chloride injection for maintaining patency of indwelling intermittent infusion devices.

In a double-blind study, heparin sodium was compared with 0.9% sodium chloride injection for use in maintaining patency of indwelling devices for intermittent intravenous infusion. Adult patients who required intermittent intravenous devices were randomly assigned to receive 1 mL of a heparin sodium 100 units/mL flush solution or a 0.9% sodium chloride flush solution. Observations were recorded for each catheter, rather than for each patient. Patients were evaluated daily for the development of phlebitis. In the 160 patients for whom complete data on catheter patency were available, there were 307 observations (170 for the heparin group and 137 for the sodium chloride group). No significant difference in the duration of catheter patency or incidence of phlebitis was observed between the groups. A difference in the incidence of phlebitis could not be excluded with confidence, but inasmuch as there was no effect on duration of catheter patency, the clinical importance of this superficial venous phlebitis is questionable. The duration of patency was significantly greater in men than in women. The use of penicillins, cephalosporins, or clindamycin, alone or in combination, was significantly associated with the development of phlebitis for both treatment groups. No other factors were found to correlate with either the duration of catheter patency or incidence of phlebitis. The results of this study indicate that heparin offers no advantage over 0.9% sodium chloride injection in maintaining the patency of intermittent intravenous devices.

Adult↗
PubMed1987

[Orbital localization of clear-cell sarcoma of tendons and aponeuroses. Apropos of a case report].

Clear cell sarcoma of tendons and aponeuroses actually is a well identified soft tissue tumor. A primary orbital involvement is presented, with an optical and electron microscopic study. The orbital topography of such a tumor seems to be an exceptional opportunity. The histological study showed the typical pattern of this clear cell tumor. Ultrastructurally, there are not absolute specific features to establish the diagnosis, except the finding of intra-cellular melanosomes. Histogenesis has been debated for a long time between a melanotic or a synovial origin. According to present knowledge, this tumor may be attributed to a neural crest origin.

Adult↗
PubMed1986

[Corneal dysplasia].

Corneal dysplasia has been recently reported. Clinically, it is characterized by a progressive epithelial corneal opacity with pearly or greyish white coloration. Its topography may be either next to either far from the limbus. The recurrences are frequent after surgical treatment. Histologically, many aspects are described. Morphological changes affecting the cells and/or the architecture of the modified epithelium, may vary from light dysplasia to true carcinoma in situ. Some peculiar clinical conditions may coexist with corneal dysplasia, which may also be isolated. Three clinical cases are reported, with detailed pathological data. The signification of the use of the term "dysplasia" and the histogenesis are discussed, and the conclusions for treatment are drawn.

Carcinoma in Situ↗
PubMed1984

Behavior analysis in consumer affairs: Retail and consumer response to publicizing food price information.

A popular program among consumer action groups involves publicizing comparative food price information (CFPI) gathered from retail stores. Its significance is based on the assumption that publishing CFPI maximizes retail competition (i.e., moderates price levels or price increases) and occasions more frugal store selections among consumers. We tested these assumptions during a 2-year analysis. Specifically, we monitored the prices of two distinct market baskets in the supermarkets of two midwestern cities (target and contrast cities). Following a lengthy baseline, we published the prices of only one of the market baskets at stores in the target city in the local newspaper on five different occasions. The results suggested that reductions in price inflation occurred for both market baskets at the independently operated target stores. The corporate chain stores were not similarly affected. In addition, surveys indicated that many consumers used the CFPI as a basis for store selection. Finally, the analysis included a discussion of the politics, economics, and future of CFPI programs.

Journal Article↗
PubMed1984

[Keratomycosis and keratoplasty].

Three cases of corneal perforation in keratomycosis are reported. In the first two cases the etiological diagnosis had been made from the anatomo-pathological examination of the excised corneal buttons. The mycotic origin in the third case was known before perforation from corneal cultures. Although the prognosis of this condition is usually poor, the post-keratoplasty evolution in the three cases was uncomplicated. The authors analyse the peculiarities of corneal mycotic abscess and discuss the appropriate diagnostic approach and management. Treatment must be performed before intraocular mycotic invasion occurs, because of the poor intraocular diffusion of antifungal agents. In this case, penetrating keratoplasty is not as dangerous as previously reported; and moreover, allows simultaneous treatment of the mycosis and the anatomical and functional repair of the cornea.

Abscess↗