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1.
Eur J Vasc Endovasc Surg ; 51(3): 434-40, 2016 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-26810342

RESUMEN

BACKGROUND: Forty percent of patients with chronic venous insufficiency (CVI) do not wear their indicated and prescribed compression stockings. Difficulties in donning and a feeling of constraint are the most common reasons for non-adherence. OBJECTIVE: The aim was to develop a compression stocking system that is easy to don and dose adjustable. METHODS: A modular compression stocking kit composed of an understocking and three superimposable leggings (SLLLs) was developed. Substocking pressures (P) at the thinnest part above the ankle (cB level) were 17 mm (understocking) + 15 + 10 + 10 mmHg (3 superimposed leggings; Hatra method). Twenty healthy subjects and 20 patients over 65 years with CVI donned the SLLL compression kit. P was measured in vivo (Picopress method) at the transition of the Achilles tendon to the calf muscle (level cB1) during rest and ankle movements (DSI; dynamic stiffness index) and compared with a strong compression stocking of 40 mmHg (S40). RESULTS: Twenty (20/20) patients aged over 65 with CVI (C4-6) successfully donned the SLLL compression kit without aid, compared with 12 (12/20) who were able to don the S40 without aid (p = .02). In vivo resting P at level cB1 was 34.3 mmHg (SLLL) compared with 37.3 mmHg (S40) (p = .1). The DSI was 16.1 (SLLL) compared with 17.9 (p = .79; S40; CVI group). CONCLUSION: The physical properties of the SLLL compression stocking kit correspond to the characteristics of a strong stocking at rest and exercise (DSI). The donning success rate is excellent (100%). A further potential advantage is that the SLLL leg compression kit is dose adjustable, according to indication or patient tolerance. Wearing comfort over periods of several days and clinical effectiveness need to be investigated in future trials.


Asunto(s)
Pierna/irrigación sanguínea , Medias de Compresión , Insuficiencia Venosa/terapia , Anciano , Anciano de 80 o más Años , Diseño de Equipo , Femenino , Humanos , Masculino , Presión
3.
Eur J Vasc Endovasc Surg ; 49(2): 221-9, 2015 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-25579875

RESUMEN

OBJECTIVE/BACKGROUND: Compression therapy is highly effective in the treatment of post-thrombotic syndrome and venous leg ulcer. On average, 50-60% of the patients cooperate with compression therapy. Therefore, it is necessary to improve the user-friendliness. This prospective study investigated whether the use of donning devices can contribute to improving user-friendliness. METHODS: Forty patients aged >65 years with severe chronic venous insufficiency (CVI; C4-C6) successively donned compression stockings in a randomized order: one 40 mmHg (CS40) or two superimposed 20 mmHg (CS20+20), each with open toe (CS-o-t) and closed toe (CS-c-t), using donning devices (three foot slips for CS-o-t; two foot slips and three frames for CS-c-t). The study endpoint was that the stocking was completely donned and correctly positioned on the patient's leg. The success rate and its association with age, sex, first time versus second time user, body mass index, abdominal circumference, ability to reach the forefoot with the hand, and hand grip strength were analyzed. Additionally, subjective evaluation by the patients was performed. RESULTS: Without donning devices, success with CS40-c-t was 60% (24/40 patients) and with CS20+20-c-t 70% (28/40 patients) (p = .220). Using donning devices increased success rates significantly. With CS40-o-t the success rate was 88% (35/40 patients; p = .001) and with CS40-c-t it was 90% (36/40 patients; p = .002). With CS20+20-o-t and CS20+20-c-t, the success rate was 88% (35/40 patients; p = .016). The proportion of patients who successfully used either CS40 or CS20+20 increased from 73% to 93%. Relevant for the patients' success was the ability to reach the forefoot with the hand, and hand grip strength. Subjectively, donning with a device was rated significantly better than without. CONCLUSION: Donning devices significantly improve the ability of elderly patients with CVI to don compression stockings successfully. However, there are differences in user-friendliness among the devices..


Asunto(s)
Cooperación del Paciente , Autocuidado/instrumentación , Dispositivos de Autoayuda , Medias de Compresión , Insuficiencia Venosa/terapia , Factores de Edad , Anciano , Anciano de 80 o más Años , Enfermedad Crónica , Diseño de Equipo , Femenino , Humanos , Masculino , Satisfacción del Paciente , Estudios Prospectivos , Índice de Severidad de la Enfermedad , Suiza , Resultado del Tratamiento , Insuficiencia Venosa/diagnóstico
4.
Zentralbl Chir ; 140(5): 542-6, 2015 Oct.
Artículo en Alemán | MEDLINE | ID: mdl-25333521

RESUMEN

Martorell hypertensive ischaemic leg ulcer (HYTILU) represents an important differential diagnosis of painful leg ulcerations. Stenotic subcutaneous arteriolosclerosis in patients with long-standing arterial hypertension finally leads to skin infarction. The typical histological changes are very similar in Martorell HYTILU and calciphylaxis. This raises the hypothesis that the two entities may have a common pathogenesis. Martorell HYTILU presents as an extremely painful ulcer that is regularly located at the laterodorsal lower leg or at the Achilles tendon. Because of its inflammatory and violaceous wound edges and its tendency to progression, clinicians unaware of the diagnosis Martorell HYTILU might misdiagnose pyoderma gangrenosum or necrotising cutaneous vasculitis start an immunosuppressive treatment and avoid surgical diagnostic and therapeutic procedures. Instead, necrosectomy and split skin grafting are the treatment of choice for Martorell HYTILU.


Asunto(s)
Hipertensión/complicaciones , Isquemia/diagnóstico , Isquemia/cirugía , Úlcera de la Pierna/diagnóstico , Úlcera de la Pierna/etiología , Úlcera de la Pierna/cirugía , Pierna/irrigación sanguínea , Desbridamiento , Diagnóstico Diferencial , Humanos , Colgajos Quirúrgicos/estadística & datos numéricos
5.
Br J Dermatol ; 171(5): 1066-72, 2014 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-24974741

RESUMEN

BACKGROUND: Basal cell carcinoma (BCC) is the most frequent skin cancer with increasing incidence and generally high cure rates. BCC can be quite aggressive and is difficult to treat. OBJECTIVES: To investigate BCCs with a focus on histological subtypes, treatment procedures and correlation to clinical progress to collect further information on complex BCC cases. METHODS: In this retrospective single-centre analysis the dermatopathology database, a network of cooperating dermatological surgeons, was queried for BCC cases between January 2007 and December 2011. Of 14,423 samples from a total of 9652 patients initially identified, 2938 patients were treated at the University Hospital Zurich and had corresponding local electronic patient records. RESULTS: Patients (n = 2938) (with 4769 diagnoses, 2006 re-excisions with 1180 microscopically controlled surgeries) were classified based on severity estimations into 2240 simple, 640 moderate, and 58 severe cases, including one BCC-treatment-associated death and 11 patients with subsequent participation in a clinical trial. In moderate and severe cases (n = 698), there were significantly higher rates of unique histological diagnoses (n = 2·5; P < 0·0001), higher association with basosquamous carcinoma [odds ratio (OR) 3·6; P < 0·0001] and sclerosing BCC (OR 2·48; P < 0·0001). Of the patients with basosquamous carcinoma 82·6% had a previous history of BCC. CONCLUSIONS: This is the first study that analyses the frequency of complicated BCCs in a tertiary referral centre. There were 6·6% moderate (640 of 9652) and 0·6% (58 of 9652) severe cases. We found significantly more varying histological diagnoses and significant association with aggressive subtypes in moderate and severe cases. These patients might especially benefit from new therapeutic options.


Asunto(s)
Carcinoma Basocelular/cirugía , Neoplasias Cutáneas/cirugía , Adulto , Anciano , Anciano de 80 o más Años , Carcinoma Basocelular/patología , Femenino , Alemania , Hospitalización , Humanos , Masculino , Persona de Mediana Edad , Cirugía de Mohs/estadística & datos numéricos , Estudios Retrospectivos , Neoplasias Cutáneas/patología , Centros de Atención Terciaria
7.
J Chem Phys ; 138(12): 124703, 2013 Mar 28.
Artículo en Inglés | MEDLINE | ID: mdl-23556738

RESUMEN

The polar threefold surfaces of the GaPd compound crystallizing in the B20 (FeSi-type) structure (space group P2(1)3) have been investigated using density-functional methods. Because of the lack of inversion symmetry the B20 structure exists in two enantiomorphic forms denoted as A and B. The threefold {111} surfaces have polar character. In both nonequivalent (111) and (111) directions several surface terminations differing in structure and chemical composition are possible. The formation of the threefold surfaces has been studied by simulated cleavage experiments and by calculations of the surface energies. Because of the polar character of the threefold surfaces calculations for stoichiometric slabs permit only the determination of the average energy of the surfaces exposed on both sides of the slab. Calculations for nonstoichiometric slabs performed in the grand canonical ensemble yield differences of the surface energies for the possible terminations as a function of the chemical potential in the reactive atmosphere above the surface and predict a transition between Ga- and Pd-terminated surfaces as a function of the chemical potential. The {100} surfaces are stoichiometric and uniquely defined. The calculated surface energies are identical to the average energies of the {100} surfaces of the pure metals. The {210} surfaces are also stoichiometric, with an energy very close to that of the {100} surfaces. Assuming that for the {111} surfaces the energies of different possible terminations are in a proportion equal to that of the concentration-weighted energies of the {111} surfaces of the pure metals, surface energies for all possible {111} terminations may be calculated. The preferable termination perpendicular to the A<111> direction consists of a bilayer with three Ga atoms in the upper and three Pd atoms in the lower part. The surface energy of this termination further decreases if the Pd triplet is covered by additional Ga atom. Perpendicular to the A<111> direction the lowest energy has been found for a bilayer with three Ga atoms per surface cell in the upper layer and one Ga and one Pd in the lower part. The calculated surface energies are in agreement with a simulated cleavage experiment. However, cleavage does not result in the formation of the lowest-energy surfaces, because all possible {111} cleavage planes expose a low-energy surface on one, and a high-energy surface on the other side. The prediction of Ga-terminated surfaces has been tested against the available experimental information. The calculated surface electronic density of states is in very good agreement with photo-emission spectroscopy. Calculated STM images of the most stable surfaces agree with all details of the available experimental images. The chemical reactivity of the most stable surfaces has been studied by the adsorption of CO molecules. The adsorption energies and maximum coverages calculated for the Ga-terminated surfaces permit a reasonable interpretation of the observed thermal desorption spectra, whereas for the Pd-terminated surfaces the calculated adsorption energies are far too high.

8.
Hautarzt ; 64(12): 917-22, 2013 Dec.
Artículo en Alemán | MEDLINE | ID: mdl-24077917

RESUMEN

BACKGROUND: Leg ulcers are a symptom of a heterogeneous group of diseases. Their treatment causes substantial costs due to the long healing times and extensive wound care measures. There is a paucity of information about healing times and the necessity of hospital treatment for leg ulcers of different etiologies. MATERIALS AND METHODS: In this retrospective study, healing times and the frequency of in-hospital treatment of 355 patients with leg ulcers attending a wound care clinic of a university hospital were examined. RESULTS: The proportion of healed ulcers was 32.0% after 3 months and 54.3% after 6 months with an average treatment duration of 6.1 months for all ulcers. This proportion of healed ulcers was higher for venous ulcers with 45.5% after 3 months and 63.0% after 6 months, whereas only 30.0% of mixed arterial-venous ulcers and 35.0% of hypertensive ischemic leg ulcers (HYTILU) were healed after 6 months. Of the latter group, 71% of patients were hospitalized at least once during the observation period as compared to 47% of patients with a venous ulcer. The duration of the hospital stay was longer for mixed ulcers and HYTILU with an average of 30 days vs. 23 days for venous ulcers. CONCLUSIONS: These data indicate that the healing times of ulcers of different etiologies differ substantially and that especially ulcers with arteriosclerosis as a causative factor have longer healing times. The fact that they require in-hospital treatment more frequently and for longer periods has significant socio-economic consequences.


Asunto(s)
Hospitalización/estadística & datos numéricos , Úlcera de la Pierna/terapia , Recuperación de la Función , Cicatrización de Heridas , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Úlcera de la Pierna/diagnóstico , Masculino , Persona de Mediana Edad , Prevalencia , Estudios Retrospectivos , Suiza/epidemiología , Factores de Tiempo , Resultado del Tratamiento
9.
Br J Dermatol ; 166(2): 422-4, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-21895616

RESUMEN

BACKGROUND: Recent studies suggest that patients on mammalian target of rapamycin (mTOR) inhibitors experience a reduction in cutaneous carcinogenesis by an estimated 50% or more compared with calcineurin inhibitors. While randomized trials are running, organ transplant recipients are frequently switched from calcineurin inhibitors to mTOR inhibitors when cutaneous carcinogenesis increases. OBJECTIVES: To slow carcinogenesis in our patient, a heart transplant recipient with a neuropathic diabetic foot syndrome who had developed cutaneous carcinogenesis at a rate of more than 20 squamous cell carcinomas (SCC) annually. METHODS: The patient's immunosuppression was switched from the calcineurin inhibitor ciclosporin to the mTOR inhibitor everolimus. RESULTS: Carcinogenesis slowed to six SCC annually; however, he developed recalcitrant diabetic foot ulcers which were purely neuropathic and nonangiopathic, and a limb-threatening fistulating necrotic erysipelas of the right leg. Both sites responded poorly to antibiotic therapy, offloading and debridement. This skin fistula became chronic and some toes were at risk for minor amputation. In view of the propensity for mTOR inhibitors to impair would healing, immunosuppression was switched back to ciclosporin. All wounds healed rapidly, but skin carcinogenesis rose to former levels. CONCLUSIONS: This case impressively illustrates the clinical dilemma for mTOR inhibitor use where benefit in carcinogenesis is counterbalanced by impairment in wound healing. Changes in immunosuppressive regimens should thus be made on an individual basis with careful consideration of the relative risks.


Asunto(s)
Pie Diabético/fisiopatología , Inmunosupresores/efectos adversos , Neoplasias Cutáneas/prevención & control , Serina-Treonina Quinasas TOR/antagonistas & inhibidores , Cicatrización de Heridas/efectos de los fármacos , Anciano , Inhibidores de la Calcineurina , Cardiomiopatía Dilatada/cirugía , Transformación Celular Neoplásica/efectos de los fármacos , Sustitución de Medicamentos , Everolimus , Trasplante de Corazón , Humanos , Masculino , Sirolimus/efectos adversos , Sirolimus/análogos & derivados , Sirolimus/antagonistas & inhibidores , Dedos del Pie
10.
J Wound Care ; 21(5): 228, 230, 232-3, 2012 May.
Artículo en Inglés | MEDLINE | ID: mdl-22584740

RESUMEN

OBJECTIVE: To evaluate the efficacy of a plant-derived wound dressing, a mixture of hypericum oil (Hypericum perforatum) and neem oil (Azadirachta indica), in scalp wounds with exposed bone. METHOD: A retrospective review was conducted of all patients presenting with scalp wounds with exposed bone following the excision of skin tumours and treated with a plant-derived wound dressings (1 Primary Wound Dressing; Phytoceuticals AG), from January to July 2011. Time to healing, wound size, area of exposed bone, ease of handling, pain and complications were evaluated. RESULTS: Nine consecutive patients were analysed retrospectively. The patients' mean age was 81.2 ± 8.5 years (63-90 years), with a mean wound size of 13.2 ± 6.8cm(2) (0.4-22.6cm(2)) and 6.8 ± 6.5cm(2) (0.3-20.7cm(2)) of exposed bone. The time to complete healing by secondary intention was 4-20 weeks. A rapid induction of granulation tissue was observed, which covered the entire exposed bone surface in six out of nine cases (67%) after 4 weeks, and showed a reduction in the mean area of exposed bone of 95%. Dressing change was easy and without pain and there were no complications. CONCLUSION: This retrospective, non-controlled analysis suggests that ONE is a very simple to use, safe and potentially effective therapy for the treatment of scalp wounds with exposed bone. DECLARATION OF INTEREST: There were no external sources of funding for this study. The authors have no conflict of interest to declare.


Asunto(s)
Azadirachta , Neoplasias de Cabeza y Cuello/cirugía , Hypericum , Fitoterapia , Aceites de Plantas/uso terapéutico , Complicaciones Posoperatorias/tratamiento farmacológico , Cuero Cabelludo/lesiones , Neoplasias Cutáneas/cirugía , Heridas no Penetrantes/tratamiento farmacológico , Anciano , Anciano de 80 o más Años , Quimioterapia Combinada , Femenino , Humanos , Persona de Mediana Edad , Cráneo
11.
Clin Exp Immunol ; 163(3): 324-32, 2011 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-21175594

RESUMEN

Selection of suitable antigens is critical for the development of cancer vaccines. Most desirable are over-expressed cell surface proteins that may serve as targets for both antibodies and T cells, thus maximizing a concerted immune response. Towards this goal, we characterized the relevance of tumour necrosis factor-α-converting enzyme (ADAM17) for such targeted therapeutics. ADAM17 is one of the several metalloproteinases that play a key role in epidermal growth factor receptor (EGFR) signalling and has recently emerged as a new therapeutic target in several tumour types. In the present study, we analysed the expression profile of ADAM17 in a variety of normal and cancer cells of human origin and found that this protein is over-expressed on the surface of several types of cancer cells compared to the normal counterparts. Furthermore, we analysed the presentation of a human leucocyte antigen (HLA)-A2-restricted epitope from ADAM17 protein to specific T cells established from normal donors as well as ovarian cancer patients. Our analysis revealed that the HLA-A2-restricted epitope is processed efficiently and presented by various cancer cells and not by normal cells. Tumour-specific T cell activation results in the secretion of both interferon-γ and granzyme B that can be blocked by HLA-A2 specific antibodies. Collectively, our data present evidence that ADAM17 can be a potential target antigen to devise novel immunotherapeutic strategies against ovarian, breast and prostate cancer.


Asunto(s)
Proteínas ADAM/inmunología , Neoplasias de la Mama/inmunología , Antígenos de Histocompatibilidad Clase I/inmunología , Inmunoterapia , Neoplasias Ováricas/inmunología , Neoplasias de la Próstata/inmunología , Proteínas ADAM/genética , Proteínas ADAM/metabolismo , Proteína ADAM17 , Presentación de Antígeno/inmunología , Antígenos de Neoplasias/genética , Antígenos de Neoplasias/inmunología , Antígenos de Neoplasias/metabolismo , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/terapia , Línea Celular Tumoral , Epítopos de Linfocito T/inmunología , Femenino , Expresión Génica/genética , Regulación Neoplásica de la Expresión Génica/fisiología , Granzimas/metabolismo , Antígeno HLA-A2/inmunología , Humanos , Interferón gamma/metabolismo , Leucocitos Mononucleares/inmunología , Activación de Linfocitos/inmunología , Masculino , Proteínas de la Membrana/genética , Proteínas de la Membrana/inmunología , Proteínas de la Membrana/metabolismo , Neoplasias Ováricas/metabolismo , Neoplasias Ováricas/terapia , Fragmentos de Péptidos/inmunología , Neoplasias de la Próstata/metabolismo , Neoplasias de la Próstata/terapia , Linfocitos T/inmunología , Linfocitos T/metabolismo , Linfocitos T Citotóxicos/inmunología , Linfocitos T Citotóxicos/metabolismo
12.
J Eur Acad Dermatol Venereol ; 25(4): 441-6, 2011 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-20659308

RESUMEN

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading strains among multiresistant hospital microflora. In 2003, we noted an increase in the number of MRSA strain 35 among patients at the University of Zurich, Department of Dermatology. At the end of 2003, we implemented additional policies in hospital hygiene, which significantly decreased the number of MRSA infections. METHODS: This is a retrospective study on 65 consecutive patients at the Department of Dermatology, University Hospital of Zurich, in whom MRSA contamination was newly diagnosed during the period of 2003-2008. All isolated strains were genotyped. We implemented additional policies as strict hand hygiene and avoidance of sharing the same ointment pots or tubes amongst patients. As soon as the skin disease was healed, decolonization of MRSA was undertaken by a 5-day topical treatment. RESULTS: Of the 65 MRSA patients, 19 (29%) patients carried a genotypical strain (MRSA 35) that was identified to be specific for the Department of Dermatology. Three health care workers (HCWs) were tested positive. The outlined measures reduced the incidence of new transmissions of this specific strain MRSA 35 significantly (P=0.001) with a complete disappearance of new transmissions of MRSA 35 in the year 2008. Of the 65 patients, 15 (23%) patients became long-term carriers, among all (15/15; 100%) had persisting active skin lesions. CONCLUSIONS: Strict hand hygiene and avoidance of sharing ointments among patients were highly effective measures in controlling an outbreak of MRSA. Complete of near-to-complete remission of the underlying dermatoses, skin lesions or chronic wounds, is a prerequisite for complete decolonization of MRSA carriers.


Asunto(s)
Dermatología , Brotes de Enfermedades , Hospitales Universitarios/organización & administración , Staphylococcus aureus Resistente a Meticilina/aislamiento & purificación , Infecciones Estafilocócicas/prevención & control , Humanos , Incidencia , Infecciones Estafilocócicas/epidemiología , Infecciones Estafilocócicas/microbiología , Suiza/epidemiología
14.
Nanotechnology ; 21(8): 85102, 2010 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-20097970

RESUMEN

Combining diagnostic and therapeutic processes into one (theranostics) and improving their selectivity to the cellular level may offer significant benefits in various research and disease systems and currently is not supported with efficient methods and agents. We have developed a novel method based on the gold nanoparticle-generated transient photothermal vapor nanobubbles, that we refer to as plasmonic nanobubbles (PNB). After delivery and clusterization of the gold nanoparticles (NP) to the target cells the intracellular PNBs were optically generated and controlled through the laser fluence. The PNB action was tuned in individual living cells from non-invasive high-sensitive imaging at lower fluence to disruption of the cellular membrane at higher fluence. We have achieved non-invasive 50-fold amplification of the optical scattering amplitude with the PNBs (relative to that of NPs), selective mechanical and fast damage to specific cells with bigger PNBs, and optical guidance of the damage through the damage-specific signals of the bubbles. Thus the PNBs acted as tunable theranostic agents at the cellular level and in one process that have supported diagnosis, therapy and guidance of the therapy.


Asunto(s)
Sistemas de Liberación de Medicamentos/métodos , Nanopartículas del Metal/administración & dosificación , Microburbujas , Nanotecnología/métodos , Medicina de Precisión/métodos , Línea Celular Tumoral , Oro/administración & dosificación , Humanos , Rayos Láser , Neoplasias/diagnóstico , Neoplasias/tratamiento farmacológico , Neoplasias/patología
15.
Nanotechnology ; 21(22): 225102, 2010 Jun 04.
Artículo en Inglés | MEDLINE | ID: mdl-20453288

RESUMEN

The zebrafish embryo has been evaluated as an in vivo model for plasmonic nanobubble (PNB) generation and detection at nanoscale. The embryo is easily observed and manipulated utilizing the same methodology as for application of PNBs in vitro. Injection and irradiation of gold nanoparticles with a short laser pulse resulted in generation of PNBs in zebrafish with similar parameters as for PNBs generated in water and cultured living cells. These PNBs do not result in systemic damage, thus we demonstrated an in vivo model for rapid and precise testing of plasmonic nanotechnologies.


Asunto(s)
Nanopartículas del Metal/química , Microburbujas , Pez Cebra/metabolismo , Animales , Línea Celular Tumoral , Embrión no Mamífero/química , Oro/química , Oro/farmacocinética , Oro/uso terapéutico , Humanos , Luz , Neoplasias Pulmonares/química , Neoplasias Pulmonares/metabolismo , Nanopartículas del Metal/uso terapéutico , Microscopía , Modelos Animales , Nanotecnología/métodos , Dispersión de Radiación , Pez Cebra/embriología
16.
Science ; 291(5502): 283-5, 2001 Jan 12.
Artículo en Inglés | MEDLINE | ID: mdl-11209073

RESUMEN

We report the characterization of defects in individual metallic single-walled carbon nanotubes by transport measurements and scanned gate microscopy. A sizable fraction of metallic nanotubes grown by chemical vapor deposition exhibits strongly gate voltage-dependent resistance at room temperature. Scanned gate measurements reveal that this behavior originates from resonant electron scattering by defects in the nanotube as the Fermi level is varied by the gate voltage. The reflection coefficient at the peak of a scattering resonance was determined to be about 0.5 at room temperature. An intratube quantum dot device formed by two defects is demonstrated by low-temperature transport measurements.


Asunto(s)
Carbono/química , Electrones , Conductividad Eléctrica , Impedancia Eléctrica , Microscopía , Semiconductores , Temperatura
17.
Science ; 269(5230): 1550-3, 1995 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-17789445

RESUMEN

Field emission of electrons from individually mounted carbon nanotubes has been found to be dramatically enhanced when the nanotube tips are opened by laser evaporation or oxidative etching. Emission currents of 0.1 to 1 microampere were readily obtained at room temperature with bias voltages of less than 80 volts. The emitting structures are concluded to be linear chains of carbon atoms, Cn, (n = 10 to 100), pulled out from the open edges of the graphene wall layers of the nanotube by the force of the electric field, in a process that resembles unraveling the sleeve of a sweater.

18.
Science ; 266(5188): 1218-22, 1994 Nov 18.
Artículo en Inglés | MEDLINE | ID: mdl-17810264

RESUMEN

Carbon nanotubes produced in arcs have been found to have the form of multiwalled fullerenes, at least over short lengths. Sintering of the tubes to each other is the predominant source of defects that limit the utility of these otherwise perfect fullerene structures. The use of a water-cooled copper cathode minimized such defects, permitting nanotubes longer than 40 micrometers to be attached to macroscopic electrodes and extracted from the bulk deposit. A detailed mechanism that features the high electric field at (and field-emission from) open nanotube tips exposed to the arc plasma, and consequent positive feedback effects from the neutral gas and plasma, is proposed for tube growth in such arcs.

19.
Tob Control ; 18(6): 451-8, 2009 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19700437

RESUMEN

BACKGROUND: The adoption of a smoke-free hospital campus policy is often a highly publicised local event. National media coverage suggests that the trend towards adopting these policies is growing, and this publicity can frequently lead hospital administrators to consider the adoption of such policies within their own institutions. Little is actually known, however, about the prevalence of these policies or their impact. OBJECTIVES: To determine the national prevalence of smoke-free hospital campus policies and the relation between these policies and performance on nationally standardised measures for smoking cessation counselling in US hospitals. METHODS: 4494 Joint Commission-accredited hospitals were invited to complete a web-based questionnaire assessing current smoking policies and future plans. Smoking cessation counselling rates were assessed through nationally standardised measures. RESULTS: The 1916 hospitals responding to the survey (43%) were statistically similar to non-responders with respect to performance measure rates, smoking policies and demographic characteristics. Approximately 45% of responders reported an existing smoke-free hospital campus policy. With respect to demographics, higher proportions of smoke-free campus policies were reported in non-teaching and non-profit hospitals. Smoke-free campus hospitals were also more likely to provide smoking cessation counselling to patients with acute myocardial infarction, heart failure and pneumonia who smoke (p<0.001). CONCLUSIONS: By February 2008, 45% of US hospitals (up from approximately 3% in 1992) had adopted a smoke-free campus policy; another 15% reported actively pursuing the adoption of such a policy. By the end of 2009, it is likely that the majority of US hospitals will have a smoke-free campus.


Asunto(s)
Hospitales/normas , Política Organizacional , Prevención del Hábito de Fumar , Contaminación por Humo de Tabaco/prevención & control , Consejo , Hospitales/estadística & datos numéricos , Humanos , Joint Commission on Accreditation of Healthcare Organizations , Cese del Hábito de Fumar/estadística & datos numéricos , Estados Unidos
20.
J Chem Phys ; 129(23): 234105, 2008 Dec 21.
Artículo en Inglés | MEDLINE | ID: mdl-19102524

RESUMEN

The stable crystal structure of LiBeH(3) is predicted on the basis of ab initio total-energy calculations using density-functional theory and an extended database of candidate structures and using global optimizations based on an evolutionary algorithm. At the level of density-functional theory, a CaSiO(3)_1-type structure with space group P2(1)/c, containing BeH(4) tetrahedra linked in chains, is the ground-state structure of LiBeH(3) (alpha-LiBeH(3)). It is found to be lower in energy than the structures proposed in previous studies. The analysis of the electronic structure shows that alpha-LiBeH(3) is an insulator with a band gap of about 4.84 eV and exhibits strong covalent bonding in the BeH(4) tetrahedral complexes. Calculations at finite temperatures and high pressures suggest that at T=408 K and ambient pressure a structural transition from alpha-LiBeH(3) (CaSiO(3)-type) to a YBO(3)-type structure with space group Cmcm occurs and that at a pressure of 7.1 GPa alpha-LiBeH(3) undergoes a pressure-induced structural transition from the alpha-phase to a MgSiO(3)-type structure with space group C2/c. The calculated enthalpies of formation (-45.36 and -30.12 kJ/mol H(2) without and with zero-point energy corrections) are in good agreement with the experimental result, indicating that LiBeH(3) is a potential hydrogen storage material with low activation barriers for hydrogen desorption.

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