Diode Effect in Asymmetric Double Tunnel Barriers with Single Metal Nanoclusters

Asymmetric double tunnel barriers with the center electrode being a metal cluster in the quantum regime are studied. The zero dimensionality of the clusters used and the associated quantized energy spectra are manifest in well-defined steps in the current voltage characteristic (IVC). Record high current rectification ratios of 10000 for tunneling through such clusters are demonstrated at room temperature. We are able to account for all of the experimentally observed features by modeling our double barrier structures using a combination of discrete states and charging effects for tunneling through quantum dots.Comment: 8 pages and 3 figures. Accepted for publication in Applied Physics Letters in 15 march 200

Spin Diode Based on Fe/MgO Double Tunnel Junction

We demonstrate a spin diode consisting of a semiconductor free nano-scale Fe/MgO-based double tunnel junction. The device exhibits a near perfect spin-valve effect combined with a strong diode effect. The mechanism consistent with our data is resonant tunneling through discrete states in the middle ferromagnetic layer sandwiched by tunnel barriers of different spin-dependent transparency. The observed magneto-resistance is record high, ~4000%, essentially making the structure an on/off spin-switch. This, combined with the strong diode effect, ~100, offers a new device that should be promising for such technologies as magnetic random access memory and re-programmable logic.Comment: 14 page

Clinical study to evaluate the factors involved in the evolution of the halitosis in a group of students

Halitoza este o problemă medico-socială universală, în toate comunităţile şi se referă la mirosul neplăcut care se emană din cavitatea orală. Obiectivele acestui studiu sunt: de a investiga prevalenţa halitozei evaluându-se prin mijloace clinice, paraclinice şi printr-un screening tip anchetă a prezenţei halitozei, a factorilor cauzali implicaţi: patologia cavităţii orale asociate, cum ar fi cariile dentare şi boala parodontală, practicile de igienă orală, şi bolile generale implicate, în rândul unui eşantion de studenţi de la Facultatea de Medicină Dentară UMF Gr.T. Popa. Analiza rezultatelor obţinute cu stabilitatea corespondenţei dintre percepţia propriei halitoze şi a măsurilor de igienă orală efectuate de participanţii la studiu. Caracteristicile şi etiologia respiraţiei urât mirositoare s-au analizat pe un grup de 176 de studenţi, anul III-IV de la facultatea de Medicină Dentară, care au fost supuşi unei evaluări: printr-un chestionar standard şi un examen clinic odonto-parodontal complet, inclusiv a unui examen paraclinic cu un dispozitiv portabil (Detector de halenă ), stabilindu-se punctajele organoleptice măsurate.Halitosis is a universal medical and social problem in all communities and refers to the bad odor that emanates from the oral cavity. The objectives of this study are: to investigate the prevalence of the Halitosis by clinical and laboratory methods, to determine the causal factors involved: oral cavity associated pathology such as dental caries and periodontal disease, oral hygiene practices, and general diseases involved among a sample of students from the Faculty of Dental Gr. T. Popa. Stability analysis results obtained with the correspondence between their perception of halitosis and oral hygiene measures by survey participants. Characteristics and etiology of bad breath were analyzed in a group of 176 students. They were subjected to an assessment: through a standard questionnaire and a clinical examination including a paraclinical examination with a portable device (Halitosis Detector)

Сравнительный анализ микротвёрдости эмали и дентина здоровых зубов и при флюорозе

The aim of this study was to compare the enamel and dentin microhardness of teeth with TF (Thylstup-Fejerskov) scores of 0,1,2,3 and 4, using microindentation method. In this study we used Hanemann VEB Zeiss Jena device. The results demonstrated a decrease of the microhardness of the teeth having dental fluorosis when compare with healthy teeth, but the association was statistically significant only in the internal third of the enamel of the teeth having TF scores of 2,3 and 4 and at the enamel-dentin junction of the teeth with TF 4.В этой работе исследуются микротвёрдость эмали и дентина зубов с флюорозом 1,2,3 и 4 степени (по классификации Thylstrup-Fejerskov), в сравнении с здоровыми тканями зубов. Микротвёрдость зубов исследуется по методу микроиндентации при помощи апарата Hanneman VEB Zeiss Jena. Результаты демонстрируют что твёрдость эмали и дентина зубов с флюорозом значительно снижается в различии от тех же структур при здоровых зубах, оссобенно, отмечаются статистические измeнения в внутренней 1/3 эмали и на уровне дентино-эмалевой границе

SEM STUDY OF THE INTERFACE BETWEEN THE CAVITY WALL AND COMPOSITE RESIN IN CAVITIES FILLED USING VIBRATION

Oscillation energy has been proposed in a new method to condense resin composites. The principle of this technique assumes that vibration lowers the viscosity of the resin, allowing the material to flow and easily adapt to the cavity walls, in a similar way as a flowable composite. The aim of the study was to assess the efficiency and quality of composite compaction, using one of these new devices. MATERIALS AND METHOD: The study included 20 class I cavities prepared in extracted human molars. The teeth were randomly divided into two groups of 10 cavities. Both groups were filled with composite material Filtek Z250 and the adhesive system Single Bond Plus Adhesive Adper TM Adhesive (3M ESPE).  In the control group, condensation of the composite was done with standard instruments. In the experimental group, condensation was done using a vibration instrument: Compothixo (Kerr).  The prepared sections were observed on a scanning electron microscope (SEM), VEGA II model LSH (TESCAN). RESULTS: When using Compothixo, the average working time was 8.53 min / restoration while, when using standard instruments, the average working time was 10.32 min, which seems to indicate that the vibration technique was more effective than traditional condensation. Microscopic images have shown that neither vibrating condensation nor manual condensation precluded the formation of a hiatus in some areas of the interface between the restoration and the cavity walls, especially in areas of small irregularities. CONCLUSIONS: Condensation of composite resins can be faster when using vibrating instruments. Adaptation of the material to the cavity walls is comparable to that obtained by traditional techniques

Crossover between short- And long-range proximity effects in superconductor/ferromagnet/superconductor junctions with Ni-based ferromagnets

We study superconductor/ferromagnet/superconductor junctions with CuNi, PtNi, or Ni interlayers. Remarkably, we observe that supercurrents through Ni can be significantly larger than through diluted alloys. The phenomenon is attributed to the dirtiness of disordered alloys leading to a short coherence length despite a small exchange energy. To the contrary, pure Ni is clean resulting in a coherence length as long as in a normal metal. Analysis of temperature dependencies of critical currents reveals a crossover from short (dirty) to long (clean) range proximity effects in Pt1-xNix with increasing Ni concentration. Our results point out that structural properties of a ferromagnet play a crucial role for the proximity effect and indicate that conventional strong-but-clean ferromagnets can be advantageously used in superconducting spintronic devices