Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts

©2002 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: : http://link.aip.org/link/?APPLAB/81/1869/1DOI:10.1063/1.1504867Gas sensors have been fabricated using the single-crystalline SnO₂ nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and NO₂ , as well as to ethanol for breath analyzers and food control applications. The sensor response, defined as the relative variation in conductance due to the introduction of the gas, is 4160% for 250 ppm of ethanol and 21550% for 0.5 ppm NO₂ at 400 °C. The results demonstrate the potential of fabricating nanosized sensors using the integrity of a single nanobelt with a sensitivity at the level of a few ppb

Synthesis and gas-sensing properties of pd-doped SnO2 nanocrystals. A case study of a general methodology for doping metal oxide nanocrystals

Pd-modified SnO2 nanocrystals, with a Pd/Sn nominal atomic ratio of 0.025, were prepared by injecting SnO2 sols and a Pd precursor solution into tetradecene and dodecylamine at 160 degrees C. Two different doping procedures were investigated: in co-injection, a Pd acetylacetonate solution in chloroform was mixed with the SnO2 sol before the injection; in sequential injection, the Pd solution was injected separately after the SnO2 sol. The obtained suspensions were heated at the resulting 80 degrees C temperature, then the product was collected by centrifugation and dried at 80 degrees C. When using co-injection, in the dried products PdO and Pd nanoparticles were observed by high-resolution transmission electron microscopy. Only SnO2 nanocrystals were observed in dried products prepared by sequential injection. After heat-treatment at 500 degrees C, no Pd species were observed for both doping procedures. Moreover, X-ray photoelectron spectroscopy showed that, in both the doping procedures, after heat-treatment Pd is distributed only into the SnO2 nanocrystal structure. This conclusion was reinforced by the measurement of the electrical properties of Pd-doped nanocrystals, showing a remarkable increase of the electrical resistance if compared with pure SnO2 nanocrystals. This result was interpreted as Pd insertion as a dopant inside the cassiterite lattice of tin dioxide. The addition of Pd resulted in a remarkable improvement of the gas-sensing properties, allowing the detection of carbon monoxide concentrations below 50 ppm and of very low concentrations (below 25 ppm) of other reducing gases such as ethanol and acetone

Predictive Values of Transcutaneous Oxygen Tension for Above-the-ankle Amputation in Diabetic Patients with Critical Limb Ischemia

ObjectiveTo assess the values of transcutaneous oxygen tension (TcPO2) capable of predicting above-the-ankle amputation in diabetic patients diagnosed for critical limb ischemia (CLI) according to the criteria of the TransAtlantic Inter-Society Consensus.DesignRetrospective study.MethodsFrom January 1999 to December 2003, 564 diabetic patients were consecutively hospitalized for CLI in one limb. Revascularization with angioplasty or bypass graft was performed when possible and, if not possible, prostanoid therapy was used. In patients in whom therapies did not relieve the rest pain or the gangrene was extended above the Chopart joint, an above-the-ankle-amputation was performed. After treatment TcPO2 values were evaluated in all patients at the dorsum of the foot.ResultsFifty-five (9.8%) patients underwent an above-the-ankle amputation: 22 of 420 patients who underwent angioplasty, 17 of 117 patients who underwent bypass (14.5%) and 16 of 27 patients in whom revascularization was not possible. Post-treatment TcPO2, measured by a receiver operating characteristic (ROC) curve, showed a value 34mmHg as the best threshold for determining the need for revascularization, with an area under the curve of 0.89 (95%CI 0.85–0.94).Using logistic regression analysis the probability of above-the-ankle amputation for this threshold is 9.7% and reduces to 3% for TcPO2>40mmHg.ConclusionTcPO2 levels<34mmHg indicate the need for revascularization, while for values ≥ 34<40mmHg this need appears less pressing, although there remains a considerable probability of amputation. TcPO2 levels greater than 40mmHg suggest that revascularization is dependent on the severity of tissue loss and possible morbidity caused by the procedure

Response dynamics of metal oxide gas sensors working with temperature profile protocols

Abstract In this work we present the analysis of gas sensors working in modulated temperature mode with temperature varying according to exponential law. We integrate conductometric gas sensor based on semiconducting metal oxide layers and an ad-hoc developed electronics to present a sensing system based on a single sensor featuring a degree of selectivity arising from the exploitation of response dynamics features. In particular, a set of parameters is used to summarize the deviation of the response shape from the single exponential law

Long-Term Prognosis of Diabetic Patients With Critical Limb Ischemia: A population-based cohort study

OBJECTIVE\u2014 To evaluate the long-term prognosis of critical limb ischemia (CLI) in diabetic patients. RESEARCH DESIGN AND METHODS\u2014 A total of 564 consecutive diabetic patients were hospitalized for CLI from January 1999 to December 2003; 554 were followed until December 2007. RESULTS\u2014 The mean follow-up was 5.93 1.28 years. Peripheral angioplasty (PTA) was performed in 420 (74.5%) and bypass graft (BPG) in 117 (20.6%) patients. Neither PTA nor BPG were possible in 27 (4.9%) patients. Major amputations were performed in 74 (13.4%) patients: 34 (8.2%) in PTA, 24 (21.1%) in BPG, and 16 (59.2%) in a group that received no revascularization. Restenosis occurred in 94 patients, bypass failures in 36 patients, and recurrent ulcers in 71 patients. CLI was observed in the contralateral limb of 225 (39.9%) patients; of these, 15 (6.7%) required major amputations (rate in contralateral compared with initial limb, P 0.007). At total of 276 (49.82%) patients died. The Cox model showed significant hazard ratios (HRs) for mortality with age (1.05 for 1 year [95% CI 1.03\u20131.07]), unfeasible revascularization (3.06 [1.40\u20136.70]), dialysis (3.00 [1.63\u20135.53]), cardiac disease history (1.37 [1.05\u20131.79]), and impaired ejection fraction (1.08 for 1% point [1.05\u20131.09]). CONCLUSIONS\u2014 Diabetic patients with CLI have high risks of amputation and death. In a dedicated diabetic foot center, the major amputation, ulcer recurrence, and major contralateral limb amputation rates were low. Coronary artery disease (CAD) is the leading cause of death, and in patients with CAD history the impaired ejection fraction is the major independent prognostic factor

TRH: Pathophysiologic and clinical implications

Thyrotropin releasing hormone is thought to be a tonic stimulator of the pituitary TSH secretion regulating the setpoint of the thyrotrophs to the suppressive effect of thyroid hormones. The peptide stimulates the release of normal and elevated prolactin. ACTH and GH may increase in response to exogenous TRH in pituitary ACTH and GH hypersecretion syndromes and in some extrapituitary diseases. The pathophysiological implications of extrahypothalamic TRH in humans are essentially unknown. The TSH response to TRH is nowadays widely used as a diganostic amplifier in thyroid diseases being suppressed in borderline and overt hyperthyroid states and increased in primary thyroid failure. In hypothyroid states of hypothalamic origin, TSH increases in response to exogenous TRH often with a delayed and/or exaggerated time course. But in patients with pituitary tumors and suprasellar extension TSH may also respond to TRH despite secondary hypothyroidism. This TSH increase may indicate a suprasellar cause for the secondary hypothyroidism, probably due to portal vessel occlusion. The TSH released in these cases is shown to be biologically inactive

Investigation of dopant profiles in nanosized materials by scanning transmission electron microscopy

Scanning electron microscopy is capable to provide chemical information on specimens interesting for the field of materials science and nanotechnology. The spatial resolution and the chemical information provided by incoherent imaging and detection of transmitted, forward-scattered electrons can reveal useful information about the specimen composition and microstructure. This paper discusses the capability and potential of low-voltage Scanning Transmission Electron Microscopy (STEM) for the characterization of multilayered structures and dopant profiles in crystalline materials

A prospective, double-blind, randomized, controlled clinical trial comparing standard wound care with adjunctive hyperbaric oxygen therapy (HBOT) to standard wound care only for the treatment of chronic, non-healing ulcers of the lower limb in patients with diabetes mellitus: a study protocol

<p>Abstract</p> <p>Background</p> <p>It has been suggested that the use of adjunctive hyperbaric oxygen therapy improves the healing of diabetic foot ulcers, and decreases the risk of lower extremity amputations. A limited number of studies have used a double blind approach to evaluate the efficacy of hyperbaric oxygen therapy in the treatment of diabetic ulcers. The primary aim of this study is to assess the efficacy of hyperbaric oxygen therapy plus standard wound care compared with standard wound care alone in preventing the need for major amputation in patients with diabetes mellitus and chronic ulcers of the lower limb.</p> <p>Methods/Design</p> <p>One hundred and eighteen (59 patients per arm) patients with non-healing diabetic ulcers of the lower limb, referred to the Judy Dan Research and Treatment Centre are being recruited if they are at least 18 years of age, have either Type 1 or 2 diabetes with a Wagner grading of foot lesions 2, 3 or 4 on lower limb not healing for at least 4 weeks. Patients receive hyperbaric oxygen therapy every day for 6 weeks during the treatment phase and are provided ongoing wound care and weekly assessments. Patients are required to return to the study centre every week for an additional 6 weeks of follow-up for wound evaluation and management. The primary outcome is freedom from having, or meeting the criteria for, a major amputation (below knee amputation, or metatarsal level) up to 12 weeks after randomization. The decision to amputate is made by a vascular surgeon. Other outcomes include wound healing, effectiveness, safety, healthcare resource utilization, quality of life, and cost-effectiveness. The study will run for a total of about 3 years.</p> <p>Discussion</p> <p>The results of this study will provide detailed information on the efficacy of hyperbaric oxygen therapy for the treatment of non-healing ulcers of the lower limb. This will be the first double-blind randomized controlled trial for this health technology which evaluates the efficacy of hyperbaric oxygen therapy in prevention of amputations in diabetic patients.</p> <p>Trial registration</p> <p>ClinicalTrials.gov Identifier: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00621608">NCT00621608</a></p

Prevalence and Predictors of Abnormal Cardiovascular Responses to Exercise Testing Among Individuals With Type 2 Diabetes: The Look AHEAD (Action for Health in Diabetes) study

OBJECTIVE We examined maximal graded exercise test (GXT) results in 5,783 overweight/obese men and women, aged 45–76 years, with type 2 diabetes, who were entering the Look AHEAD (Action for Health in Diabetes) study, to determine the prevalence and correlates of exercise-induced cardiac abnormalities. RESEARCH DESIGN AND METHODS Participants underwent symptom-limited maximal GXTs. Questionnaires and physical examinations were used to determine demographic, anthropometric, metabolic, and health status predictors of abnormal GXT results, which were defined as an ST segment depression ≥1.0 mm, ventricular arrhythmia, angina pectoris, poor postexercise heart rate recovery (<22 bpm reduction 2 min after exercise), or maximal exercise capacity less than 5.0 METs. Systolic blood pressure response to exercise was examined as a continuous variable, without a threshold to define abnormality. RESULTS Exercise-induced abnormalities were present in 1,303 (22.5%) participants, of which 693 (12.0%) consisted of impaired exercise capacity. ST segment depression occurred in 440 (7.6%), abnormal heart rate recovery in 206 (5.0%), angina in 63 (1.1%), and arrhythmia in 41 (0.7%). Of potential predictors, only greater age was associated with increased prevalence of all abnormalities. Other predictors were associated with some, but not all, abnormalities. Systolic blood pressure response decreased with greater age, duration of diabetes, and history of cardiovascular disease. CONCLUSIONS We found a high rate of abnormal GXT results despite careful screening for cardiovascular disease symptoms. In this cohort of overweight and obese individuals with type 2 diabetes, greater age most consistently predicted abnormal GXT. Long-term follow-up of these participants will show whether these abnormalities are clinically significant. Cardiovascular disease (CVD) risk factors improve with exercise in individuals with diabetes (1). Similarly, individuals with diabetes who are physically active or have higher fitness levels have reduced CVD incidence and mortality (2,3). Nevertheless, participation in exercise may involve risks for individuals with diabetes because of their high prevalence of CVD, including silent ischemia, and other comorbid conditions (4). Knowledge about the typical cardiovascular responses to exercise in individuals with type 2 diabetes has come mainly from small clinic-based studies (5) and a few larger studies in the general population (4,6,7). The Look AHEAD (Action for Health in Diabetes) study is a multicenter randomized clinical trial designed to evaluate the long-term effects of an intensive lifestyle intervention program of weight loss and physical activity on morbidity and mortality from CVD in overweight and obese individuals with type 2 diabetes (8). Graded exercise tests (GXTs) with electrocardiographic monitoring were conducted at baseline in 5,783 individuals, providing the largest sample of systematic stress testing ever conducted in individuals with type 2 diabetes. The aims of this analysis are to examine the range of abnormal exercise responses and to examine the degree to which demographic factors, health characteristics, and medication use associate with abnormal exercise responses. Identifying predictors from readily available demographic and clinical data may assist risk stratification before exercise testing or exercise prescription for individuals with diabetes

Long-Term Outcomes of Diabetic Patients With Critical Limb Ischemia Followed in a Tertiary Referral Diabetic Foot Clinic

We describe the long-term outcomes of 510 diabetic patients with critical limb ischemia (CLI) and an active foot ulcer or gangrene, seen at the University Hospital of Rome Tor Vergata, a tertiary care clinic