A highly responsive NH3 sensor based on Pd-loaded ZnO nanoparticles prepared via a chemical precipitation approach.

The gas-detecting ability of nanostructured ZnO has led to significant attention being paid to the development of a unique and effective approach to its synthesis. However, its poor sensitivity, cross-sensitivity to humidity, long response/recovery times and poor selectivity hinder its practical use in environmental and health monitoring. In this context, the addition of noble metals, as dopants or catalysts to modify the ZnO surface has been examined to enhance its sensing performance. Herein, we report preparation of Pd-loaded ZnO nanoparticles via a chemical precipitation approach. Various Pd loadings were employed to produce surface-modified ZnO nanostructure sensors, and their resulting NH3 sensing capabilities both in dry and humid environments were investigated. Through a comparative gas sensing study between the pure and Pd-loaded ZnO sensors upon exposure to NH3 at an optimal operating temperature of 350 °C, the Pd-loaded ZnO sensors were found to exhibit enhanced sensor responses and fast response/recovery times. The influence of Pd loading and its successful incorporation into ZnO nanostructure was examined by X-ray diffraction, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy. XPS studies demonstrated that in all samples, Pd existed in two chemical states, namely Pd° and Pd2+. The possible sensing mechanism related to NH3 gas is also discussed in detail.

Treatment of presumptive primary immune-mediated thrombocytopenia with mycophenolate mofetil versus cyclosporine in dogs.

OBJECTIVES: The objective of this study was to compare hospitalisation duration, survival times, adverse events and cost of therapy in dogs with presumptive primary immune-mediated thrombocytopenia undergoing therapy with mycophenolate mofetil and corticosteroids versus cyclosporine and corticosteroids. METHODS: A retrospective study of medical case records of dogs with presumed primary immune-mediated thrombocytopenia was conducted. Data collected included signalment, presenting complaints, haematologic and biochemical profiles, vector-borne disease testing, thoracic and abdominal radiographs, abdominal ultrasound, medications administered, duration of hospitalisation, 30- and 60-day survival, adverse events and cost of therapy. Variables were compared between dogs treated solely with mycophenolate mofetil and corticosteroids or cyclosporine and corticosteroids. RESULTS: A total of 55 dogs with primary immune-mediated thrombocytopenia were identified. Eighteen were excluded because multiple immunosuppressive medications were used during treatment. Hospitalisation times, 30-day survival and 60-day survival times were similar between both groups. Dogs in the mycophenolate mofetil/corticosteroid group experienced fewer adverse events than the cyclosporine/corticosteroid group. Therapy with mycophenolate mofetil was less expensive than that with cyclosporine. CLINICAL SIGNIFICANCE: These results suggest that using the combination of mycophenolate mofetil and corticosteroids appears to be as effective as cyclosporine and corticosteroids in the treatment of presumed primary immune-mediated thrombocytopenia in dogs. Adverse events were less common and cost of therapy was lower in the mycophenolate mofetil group. Additional larger prospective, controlled, double-masked, outcome-based, multi-institutional studies are required to substantiate these preliminary findings.

On the effect of an error in a standard D2O-moderated 252Cf energy spectrum.

There appears to be an error in the neutron fluence for neutrons with energies between 9 and 10 MeV for the tabulated D2O-moderated Cf source in ISO 8529-1. If the referenced spectrum is used as tabulated, the error contributes a total error to neutron dose values from this source of approximately 3%.

Effect of deposition pressure on the morphology and structural properties of carbon nanotubes synthesized by hot-filament chemical vapor deposition.

Hot-filament chemical vapor deposition has developed into an attractive method for the synthesis of various carbon nanostructures, including carbon nanotubes. This is primarily due to its versatility, low cost, repeatability, up-scalability, and ease of production. The resulting nano-material synthesized by this technique is dependent on the deposition conditions which can be easily controlled. In this paper we report on the effect of the deposition pressure on the structural properties and morphology of carbon nanotubes synthesized by hot-filament chemical vapor deposition, using Raman spectroscopy and high-resolution scanning electron microscopy, respectively. A 10 nm-thick Ni layer, deposited on a SiO2/Si substrate, was used as catalyst for carbon nanotube growth. Multi-walled carbon nanotubes with diameters ranging from 20-100 nm were synthesized at 500 degrees C with high structural perfection at deposition pressures between 150 and 200 Torr. Raman spectroscopy measurements confirm that the carbon nanotube deposit is homogeneous across the entire substrate area.

A useful formula for the radiological calibration laboratory.

A useful technique for determining the relationships between irradiation position and air kerma or neutron dose equivalent rate is presented. The standard geometric model (1/r2) is expanded allowing the user to include curvature in the model caused by scattered radiation. This technique applies to clean irradiation geometries that are well modeled by the standard geometric model, high-scatter geometries encountered in well irradiators, and neutron irradiation fields used to calibrate health physics instruments and personnel dosimeters. The technique, with slight modification, is also useful for determining the quality of x-ray beams. The basic equations and the implementing Excel functions are listed. In addition, several examples are presented to demonstrate the application of the technique.

The interaction of surface geometry with morphogens.

Expressions are given for the Gauss and Mean curvatures of a surface of thickness h. The two curvatures, (K and H), which are given at each point of the middle surface, are adequate to describe the surface. The sheet thickness varies with position in the middle surface bisecting the apical and basal surfaces. The definitions of K and H are in terms of radii of curvature, but such radii are not appropriate variables for determining how morphogens in the surface may couple to the geometry. More suitable expressions are developed here. Two important geometrical constraints must be satisfied, namely the famous Gauss-Bonnet theorem, and an inequality stemming from the definition of the two curvatures. It is argued that these constraints are of great usefulness in determining the form of the coupling of morphogens to the geometry. In particular, when two key morphogens suffice to determine surface geometry, explicit expressions are suggested to determine both Gauss (K) and Mean (H) curvatures as functions of invariant morphogen densities.

A model of pattern formation based on signaling pathways.

A model of pattern formation in the early embryo is presented. It is motivated by the necessary interaction of kinases and phosphatases, and in particular by the family of Wnt kinase and RPTP phosphatase signaling pathways. It is seen as complementary to the more short-range patterning of the Delta/Notch (or juxtacrine) signaling pathway.

Locoregional failure 10 years after mastectomy and adjuvant chemotherapy with or without tamoxifen without irradiation: experience of the Eastern Cooperative Oncology Group.

PURPOSE: To assess patterns of failure and how selected prognostic and treatment factors affect the risks of locoregional failure (LRF) after mastectomy in breast cancer patients with histologically involved axillary nodes treated with chemotherapy with or without tamoxifen without irradiation. PATIENTS AND METHODS: The study population consisted of 2,016 patients entered onto four randomized trials conducted by the Eastern Cooperative Oncology Group. The median follow-up time for patients without recurrence was 12.1 years (range, 0.07 to 19.1 years). RESULTS: A total of 1,099 patients (55%) experienced disease recurrence. The first sites of failure were as follows: isolated LRF, 254 (13%); LRF with simultaneous distant failure (DF), 166 (8%); and distant only, 679 (34%). The risk of LRF with or without simultaneous DF at 10 years was 12.9% in patients with one to three positive nodes and 28.7% for patients with four or more positive nodes. Multivariate analysis showed that increasing tumor size, increasing numbers of involved nodes, negative estrogen receptor protein status, and decreasing number of nodes examined were significant for increasing the rate of LRF with or without simultaneous DF. CONCLUSION: LRF after mastectomy is a substantial clinical problem, despite the use of chemotherapy with or without tamoxifen. Prospective randomized trials will be necessary to estimate accurately the potential disease-free and overall survival benefits of postmastectomy radiotherapy for patients in particular prognostic subgroups treated with presently used and future systemic therapy regimens.

Spatial patterning via PTP adhesive phosphatases.

Signaling pathways to the genome are a common way by which cells communicate with each other and their environment, and are often kineases or phosphatases. Patter formation is the differential spatial specification of gene activity necessary for multicellularity. It has been suspected that signaling pathways are crucial players in pattern formation in metazoans, but exactly how the pattern arise from the signaling systems has not been shown. The model discussed here is based on the protein tyrosine phosphatases, and it is shown how this important signaling system may straightforwardly produce patterns typical of early development. The protein tyrosine phosphatases have architectural characteristics basically different from those of the kinases, with the receptor tyrosine phosphatases displaying structural motifs of cell adhesion molecules. These membrane-spanning phosphatases then have a unique mission in cell growth, cell shape, and differentiation quite apart from that of the kineases. The complex intracellular biochemistry involved is modeled in the simplest way, with the intent that concepts be emphasized over biochemical detail.

Waves of pattern formation and signal pathways.

The model addresses the question of the origin of traveling waves, mimicking waves of the Hh and Dpp proteins such as found in development of the fly eye. These two proteins, which are part of an important signaling pathway to the genome, are found in a diverse array of developmental situations, for example in the formation of the proximal-distal axes in limbs. The complex intracellular biochemistry involved is modeled in the simplest way in both cases, with the intent that concepts be emphasized over biochemical detail.

Eastern Cooperative Oncology Group randomized trials of observation versus maintenance therapy for patients with metastatic breast cancer in complete remission following induction treatment.

PURPOSE: To investigate the value of maintenance treatment for patients with metastatic breast cancer whose disease is in complete remission (CR). PATIENTS AND METHODS: One hundred ninety-five women (141 eligible) whose disease was in CR or in CR except for bone metastases following six cycles (6 months) of doxorubicin-containing induction treatment were randomized to receive cyclophosphamide, methotrexate, fluorouracil, prednisone, tamoxifen, and halotestin [CMF(P)TH] or observation. In a previous pilot study, patients in CR after 24 months of induction treatment were randomized to continue chemotherapy for 4 more years or stop chemotherapy. RESULTS: Among patients randomized to CMF(P)TH, life-threatening toxicity included leukopenia in 3%, thrombocytopenia in 3%, cardiac in 2%, and diabetes in 1%. The median time to relapse from randomization was 18.7 months on CMF(P)TH and only 7.8 months on observation (P < .0001). The median time to death was 32.2 months on CMF(P)TH and 28.7 months on observation (P=.74). Similar results were seen in the pilot study (median time to relapse, 12.6 and 6.4 months; median survival, 37.7 and 24.2 months; study too small for statistical significance). Maintenance treatment was always the most significant covariate in time-to-relapse models. CONCLUSION: There is definite toxicity associated with CMF(P)TH maintenance treatment. When CR was obtained on induction, maintenance treatment with CMF(P)TH was never significant in survival models. However, maintenance treatment was always the most significant covariate in the time-to-relapse models, which motivates its consideration for appropriately informed patients.

Weekly high-dose paclitaxel in metastatic and locally advanced breast cancer: a preliminary report.

The optimal dose and schedule for paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) in the treatment of patients with advanced breast cancer are not known. Based on our phase I study in non-small cell lung cancer, in which the dose intensity of paclitaxel was successfully escalated by using a weekly schedule, we initiated a phase II study of weekly paclitaxel in previously untreated patients with metastatic breast cancer (MBC) and locally advanced breast cancer (LABC). Treatment consists of weekly paclitaxel 175 mg/m2 intravenously over 3 hours for 6 weeks, followed by a 2-week break. Doses are modified for neutropenia (absolute neutrophil count < 1,500/microL), bilirubin levels greater than 1.5 times normal, or greater than grade 1 neuropathy. Patients with MBC continue treatment until disease progression. Patients with LABC receive one to two cycles before proceeding to surgery if resectable. Thus far, 15 patients, eight with MBC and seven with LABC, are assessable for response and/or toxicity. Most patients have required dose modification, with median delivery of 75% (cycle 1) and 50% (cycle 2) of the planned dose of paclitaxel. Neutropenia has been the most common cause of dose reductions, although only one patient required treatment for neutropenic fever. Six patients have developed grade 2/3 peripheral sensory neuropathy, but with dose reductions many have continued treatment with stable or improving neurologic symptoms. Objective responses have been seen in 12 of 14 assessable patients, including six with MBC (one complete response, five partial responses) and six with LABC (two complete responses, four partial responses), for an overall response rate of 86% (95% confidence interval, 66% to 96%). All responding LABC patients have been rendered free from disease at surgery. These preliminary results are very encouraging. Accrual to the study continues.

Integrated disease control initiatives: polio eradication and neonatal tetanus elimination in Egypt.

Accelerated disease control initiatives, such as polio eradication by the year 2000, may substantially benefit public health programs in general. In Egypt, the control of other vaccine-preventable diseases, most noticeably neonatal tetanus (NT), has been facilitated by the polio eradication initiative. Linking NT reporting with the acute flaccid paralysis (AFP) surveillance system, which had been established for polio eradication, markedly improved the capacity to identify NT high-risk areas and target supplementary immunization activities appropriately. While the close integration of surveillance activities was to the benefit of both programs, mass immunization activities were not conducted simultaneously because of differences in the objectives, target populations, and operational aspects of oral polio vaccine and tetanus toxoid campaigns. In addition to substantial progress toward polio eradication in Egypt since 1988, there has been an 80% reduction in annual NT cases, in part due to the integration of appropriate aspects of these two disease control initiatives.

A model of growth and form based on adhesion molecules.

A model is given for the generation of pattern and form in living systems, based on the assumption of two types of a single adhesion molecule that form homotypic cell-cell contacts. The time dependence of the model is different from that of the Turing models, instead viewing the change in time as being driven by the change in time of the total area A, along with the sequential gene activation which is called into play at discrete times as the organism grows and changes shape. Two equations are derived on the assumption of an energy minimum equilibrium being achieved at all times on a scale that is short compared with the rate of change over time of the total area. The two equations derived from the simple assumptions of the model are the (nonlinear) Helmholtz equation and the Laplace equation. It is argued that a suitable "morphogen" should attempt to satisfy certain rather specific conditions.

Phase II study of 5-fluoruracil leucovorin and azidothymidine in patients with metastatic colorectal cancer.

The primary objective of this study was to determine the response rate of patients with metastatic colorectal cancer to combined therapy with 5-fluorouracil (5-FU), leucovorin, and intravenous azidothymidine (AZT), a thymidine nucleoside analog. By itself, AZT has limited antineoplastic efficacy. However, experimental studies indicate that 5-FU enhances the antitumor activity of AZT by inhibiting synthesis of normal thymidine nucleotides with which AZT competes for incorporation into nucleic acids. A phase I study defined the maximum tolerated dose of AZT as 7 g/m2 with hypotension during the infusion being the dose-limiting toxicity. A phase II study was performed with oral leucovorin (100 mg p.o. hourly for 4 h prior to 5-FU and 4 h and 8 h after 5-FU), bolus 5-FU (400 mg/m2) followed 1 h later by a 2-h infusion of AZT (7 g/m2). Treatment was given weekly for 4 weeks followed by a 1-week break, which constituted a cycle of therapy. Responses were evaluated after every two cycles. Patients continued on therapy as long as they tolerated treatment and did not have progressive disease. Of 15 evaluable patients who had received no chemotherapy there was 1 complete response and 4 partial responses (a 33% response rate), whereas only 1 of 6 patients who had received prior adjuvant chemotherapy had a partial response (17%). An additional 10 patients had stable disease lasting 2-14 months. Therapy was well tolerated with the only one instance each of grade 3 nausea and vomiting, diarrhea, anemia, and hypotension. Approximately 50% of treatments were accompanied by mild hypotension, which was easily corrected by increasing the rate of normal saline infusion. There was no difficulty administering this regimen in the outpatient setting. While the overall response rate (29%) is comparable to that seen with combinations of 5-FU and leucovorin alone, in most reported series a considerably higher dose of 5-FU was utilized than in this study. Since patients in the present study experienced relatively little 5-FU toxicity, increasing the dose of 5-FU in this regimen would appear to be feasible and might result in a higher response rate.