In situ electronic probing of semiconducting nanowires in an electron microscope.

For the development of electronic nanoscale structures, feedback on its electronic properties is crucial, but challenging. Here, we present a comparison of various in situ methods for electronically probing single, p-doped GaAs nanowires inside a scanning electron microscope. The methods used include (i) directly probing individual as-grown nanowires with a sharp nano-manipulator, (ii) contacting dispersed nanowires with two metal contacts and (iii) contacting dispersed nanowires with four metal contacts. For the last two cases, we compare the results obtained using conventional ex situ litho-graphy contacting techniques and by in situ, direct-write electron beam induced deposition of a metal (Pt). The comparison shows that 2-probe measurements gives consistent results also with contacts made by electron beam induced deposition, but that for 4-probe, stray deposition can be a problem for shorter nanowires. This comparative study demonstrates that the preferred in situ method depends on the required throughput and reliability.

Effect of V/III ratio on the structural and optical properties of self-catalysed GaAs nanowires.

The performance of GaAs nanowire (NW) devices depends critically on the presence of crystallographic defects in the NWs such as twinning planes and stacking faults, and considerable effort has been devoted to understanding and preventing the occurrence of these. For self-catalysed GaAs NWs grown by molecular beam epitaxy (MBE) in particular, there are in addition other types of defects that may be just as important for NW-based optoelectronic devices. These are the point defects such as the As vacancy and the Ga antisite occurring due to the inherently Ga-rich conditions of the self-catalysed growth. Here we demonstrate experimentally the effects of these point defects on the optical properties of GaAs/AlGaAs core-shell NWs grown by self-catalysed MBE. The present results enable insight into the role of the point defects both on their own and in conjunction with crystallographic planar defects.

Position-controlled uniform GaAs nanowires on silicon using nanoimprint lithography.

We report on the epitaxial growth of large-area position-controlled self-catalyzed GaAs nanowires (NWs) directly on Si by molecular beam epitaxy (MBE). Nanohole patterns are defined in a SiO2 mask on 2 in. Si wafers using nanoimprint lithography (NIL) for the growth of positioned GaAs NWs. To optimize the yield of vertical NWs the MBE growth parameter space is tuned, including Ga predeposition time, Ga and As fluxes, growth temperature, and annealing treatment prior to NW growth. In addition, a non-negligible radial growth is observed with increasing growth time and is found to be independent of the As species (i.e., As2 or As4) and the growth temperatures studied. Cross-sectional transmission electron microscopy analysis of the GaAs NW/Si substrate heterointerface reveals an epitaxial growth where NW base fills the oxide hole opening and eventually extends over the oxide mask. These findings have important implications for NW-based device designs with axial and radial p-n junctions. Finally, NIL positioned GaAs/AlGaAs core-shell heterostructured NWs are grown on Si to study the optical properties of the NWs. Room-temperature photoluminescence spectroscopy of ensembles of as-grown core-shell NWs reveals uniform and high optical quality, as required for the subsequent device applications. The combination of NIL and MBE thereby demonstrates the successful heterogeneous integration of highly uniform GaAs NWs on Si, important for fabricating high throughput, large-area position-controlled NW arrays for various optoelectronic device applications.

Controlling crystal phases in GaAs nanowires grown by Au-assisted molecular beam epitaxy.

Control of the crystal phases of GaAs nanowires (NWs) is essential to eliminate the formation of stacking faults which deteriorate the optical and electronic properties of the NWs. In addition, the ability to control the crystal phase of NWs provides an opportunity to engineer the band gap without changing the crystal material. We show that the crystal phase of GaAs NWs grown on GaAs(111)B substrates by molecular beam epitaxy using the Au-assisted vapor-liquid-solid growth mechanism can be tuned between wurtzite (WZ) and zinc blende (ZB) by changing the V/III flux ratio. As an example we demonstrate the realization of WZ GaAs NWs with a ZB GaAs insert that has been grown without changing the substrate temperature.

Management of Distal Femur Unicondylar Fractures by Calcaneal Buttress Plating: A Prospective Interventional Study.

Background: Unicondylar fracture of distal femur accounts for less than 1% of all femoral fractures. As conservative methods have shown substandard results, traditional surgical treatment includes open reduction and internal fixation by Herbert screws, cannulated screws, and conventional lateral locking plates. Though screw fixation has excellent results over long run, there is literature documenting the loosening and loss of articular congruency in elderly patients and in comminuted fracture patterns. Also, the traditional locking plates are precontoured to fit the lateral condyle, whereas there is no specific implant to fix the medial condylar fractures. The merit of the calcaneal plating is that it is easily moldable and can be used for either of the sides irrespective of fracture pattern. Objectives: This study aimed to evaluate the clinical outcome of calcaneal plate (D-shape) fixation in distal femur unicondylar fractures. Materials and Methods: A total of 30 patients were studied, who met the inclusion criteria and consented to the surgery. After appropriate investigations, these patients were treated with calcaneal plating and were followed up postoperatively at 2 weeks, 1 month, 3 months, and 6 months for clinical evaluation. Results: There was a gradual increase in the range of motion (ROM) with subsequent follow-ups. The overall mean ROM evaluated at 6 months was 108.46° ± 28.27° with P < 0.001 and was a statistically significant outcome. Also, the mean ROM for sagittal split fractures (~120°) was comparatively more than the coronally split fractures (~90°). The functional outcome assessed by Neer scoring showed excellent and satisfactory results in 24 (80%) patients, whereas the remaining six (20%) patients had poor results. None of the patients had nonunion, infection, or implant failure. Conclusion: With no specific implant for isolated unicondylar fractures, the use of calcaneal plate in our study has shown promising results probably due to its low profile design reducing the soft-tissue irritation and wide area of bone coverage by the plate offering regions of intermittent fixation due to its spanning design, thereby promoting periosteal preservation and ultimately fracture union.

Contemporary concepts in treatment planning, reconstruction and rehabilitation of the maxillofacial region: an overview of methods used in practice.

Treatment planning, reconstruction and rehabilitation of maxillofacial and dental defects have always been a challenge for a maxillofacial surgeon. Reconstruction of the oral cavity is often a difficult task as it involves the restoration of both the esthetic or cosmetic form as well as the preoperative function. Understanding the oral cavity anatomy as well the functional capacities of its various subunits is required to achieve good results. The recent advances in treatment planning, diagnostic imaging and reconstructive techniques, especially in the field of osseointegration, tissue expanders, perforator flaps, microvascular free tissue transfer and bone engineering, have yielded excellent functional and esthetic outcomes. This article provides a brief overview on various advanced reconstructive and rehabilitation techniques available in contemporary clinical practice.

Iron-Based Shape Memory Alloys in Construction: Research, Applications and Opportunities.

As a promising candidate in the construction industry, iron-based shape memory alloy (Fe-SMA) has attracted lots of attention in the engineering and metallography communities because of its foreseeable benefits including corrosion resistance, shape recovery capability, excellent plastic deformability, and outstanding fatigue resistance. Pilot applications have proved the feasibility of Fe-SMA as a highly efficient functional material in the construction sector. This paper provides a review of recent developments in research and design practice related to Fe-SMA. The basic mechanical properties are presented and compared with conventional structural steel, and some necessary explanations are given on the metallographic transformation mechanism. Newly emerged applications, such as Fe-SMA-based prestressing/strengthening techniques and seismic-resistant components/devices, are discussed. It is believed that Fe-SMA offers a wide range of applications in the construction industry but there still remains problems to be addressed and areas to be further explored. Some research needs at material-level, component-level, and system-level are highlighted in this paper. With the systematic information provided, this paper not only benefits professionals and researchers who have been working in this area for a long time and wanting to gain an in-depth understanding of the state-of-the-art, but also helps enlighten a wider audience intending to get acquainted with this exciting topic.

Correlated micro-photoluminescence and electron microscopy studies of the same individual heterostructured semiconductor nanowires.

To correlate optical properties to structural characteristics, we developed a robust strategy for characterizing the same individual heterostructured semiconductor nanowires (NWs) by alternating low temperature micro-photoluminescence (µ-PL), low voltage scanning (transmission) electron microscopy and conventional transmission electron microscopy. The NWs used in this work were wurtzite GaAs core with zinc blende GaAsSb axial insert and AlGaAs radial shell grown by molecular beam epitaxy. The series of experiments demonstrated that high energy (200 kV) electrons are detrimental for the optical properties, whereas medium energy (5-30 kV) electrons do not affect the PL response. Thus, such medium energy electrons can be used to select NWs for correlated optical-structural studies prior to µ-PL or in NW device processing. The correlation between the three main µ-PL bands and crystal phases of different compositions, present in this heterostructure, is demonstrated for selected NWs. The positions where a NW fractures during specimen preparation can considerably affect the PL spectra of the NW. The effects of crystal-phase variations and lattice defects on the optical properties are discussed. The established strategy can be applied to other nanosized electro-optical materials, and other characterization tools can be incorporated into this routine.

Wurtzite GaAs/AlGaAs core-shell nanowires grown by molecular beam epitaxy.

We report the growth of GaAs/AlGaAs core-shell nanowires (NWs) on GaAs(111)B substrates by Au-assisted molecular beam epitaxy. Electron microscopy shows the formation of a wurtzite AlGaAs shell structure both in the radial and the axial directions outside a wurtzite GaAs core. With higher Al content, a lower axial and a higher radial growth rate of the AlGaAs shell were observed. Room temperature and low temperature (4.4 K) micro-photoluminescence measurements show a much higher radiative efficiency from the GaAs core after the NW is overgrown with a radial AlGaAs shell.

Knowledge, attitude, and practice of dental implants among dental postgraduates and practitioners in Davangere City, Karnataka: A cross-sectional study.

BACKGROUND: Implant therapy has become an important part of treatment to restore function and esthetics in partially/completely edentulous patients. Inspite of the progress made in implant dentistry since its inception, there have been some loopholes in scientific based knowledge and established clinical experience amongst dental professionals and postgraduates.So,an analysis was performed of the real picture. OBJECTIVES: A study was conducted to assess and compare the knowledge, attitude and practice of dental implants among dental postgraduate students and dental practitioners (General and institutional)in Davangere City, Karnataka and to identify the variations in their knowledge, attitude and practice with respect to dentist's factors (years of experience, implant training and their specialization). MATERIALS AND METHODS: A cross sectional questionnaire based survey was conducted using census approach with informed consent. A pretested, self administered questionnaire containing demographic details and knowledge ,attitude and practice based questions was distributed and collected back from the respondents. Responses were coded before and decoded after the analysis. Statistical analysis was performed using SPSS SoftwareV17.0. RESULTS: The results were determined after the statistically analyzed and concluded that the knowledge was widespread among postgraduates and dental practitioners and variations existed amongst the subjects with respect to age, gender, years of experience, practice type, implant training and their specialization. It was also found that the attitude and practice towards implants and their evidence based knowledge about the same was variable.

Twiddler's syndrome in a patient with CRT-D device - A case report.

Twiddler's syndrome is a rare cause of pacemaker lead dislodgement. A 61-year-old female patient was implanted with a defibrillator capable of cardiac re-synchronization therapy (CRT-D); 10 months later, she presented with uneasiness and vibratory sensations in the chest. Fluoroscopy revealed rotation of the pulse generator along its longitudinal axis and dislodgement of all three leads. Diagnosis of Twiddler's syndrome was made.

Recurrent chest pain after treatment of spontaneous coronary artery dissection: An enigma.

Spontaneous coronary artery dissection (SCAD) is a rare entity. It has been described in various settings like pregnancy, collagen vascular diseases, cocaine abuse, heavy exercise, variant angina, eosinophilic arteritis, or fibro muscular dysplasia. It is also easy to miss a dissection during angiography, as the typical radiolucent lumen seen in coronary angiography may be absent in many cases. In this report, we describe the case of a 35-year-old female who presented with acute ST elevation myocardial infarction due to spontaneous coronary dissection. She had been having episodic chest pain for one year and had been seen by two different cardiologists but was thought to have non-cardiac symptoms. Even during the index hospitalization, she underwent coronary angiography three times before coronary dissection could be identified as the cause of her symptoms. She underwent coronary artery bypass graft surgery uneventfully. However, even after myocardial revascularization, she has had multiple episodes of chest pain requiring hospitalization. However, we have not been able to find a specific cause for it and the cause of her recurrent chest pain remains an enigma. This case highlights the problems, which arise while managing a case of SCAD. More research is needed to find the exact etiology and long-term prognosis of this condition.

Inducing a direct-to-pseudodirect bandgap transition in wurtzite GaAs nanowires with uniaxial stress.

Many efficient light-emitting devices and photodetectors are based on semiconductors with, respectively, a direct or indirect bandgap configuration. The less known pseudodirect bandgap configuration can be found in wurtzite (WZ) semiconductors: here electron and hole wave-functions overlap strongly but optical transitions between these states are impaired by symmetry. Switching between bandgap configurations would enable novel photonic applications but large anisotropic strain is normally needed to induce such band structure transitions. Here we show that the luminescence of WZ GaAs nanowires can be switched on and off, by inducing a reversible direct-to-pseudodirect band structure transition, under the influence of a small uniaxial stress. For the first time, we clarify the band structure of WZ GaAs, providing a conclusive picture of the energy and symmetry of the electronic states. We envisage a new generation of devices that can simultaneously serve as efficient light emitters and photodetectors by leveraging the strain degree of freedom.

Facet and in-plane crystallographic orientations of GaN nanowires grown on Si(111).

We have determined the in-plane orientation of GaN nanowires relative to the Si (111) substrate on which they were grown. We used x-ray diffraction pole figure measurements to evidence two types of crystallographic orientation, all the nanowires having [Formula: see text] lateral facets. The proportion of these two orientations was determined and shown to be influenced by the pre-deposition of Al(Ga)N intermediate layers. In the main orientation, the GaN basal [Formula: see text] directions are aligned with the [Formula: see text] directions. This orientation corresponds to an in-plane coincidence of GaN and Si lattices.

Zinc blende GaAsSb nanowires grown by molecular beam epitaxy.

We report the growth of GaAsSb nanowires (NWs) on GaAs(111)B substrates by Au-assisted molecular beam epitaxy. The structural characteristics of the GaAsSb NWs have been investigated in detail. Their Sb mole fraction was found to be about 25%. Their crystal structure was found to be pure zinc blende (ZB), in contrast to the wurtzite structure observed in GaAs NWs grown under similar conditions. The ZB GaAsSb NWs exhibit rotational twins around their [111]B growth axis, with twin-free segments as long as 500 nm. The total volumes of GaAsSb segments with twinned and un-twinned orientations, respectively, were found to be equal by x-ray diffraction analysis of NW ensembles.