126 research outputs found
Exciton-exciton interaction engineering in coupled GaN quantum dots
No full textWe present a fully three-dimensional study of the multiexciton optical response of vertically coupled GaN-based quantum dots via a direct-diagonalization approach. The proposed analysis is crucial in understanding the fundamental properties of few-particle/exciton interactions and, more important, may play an essential role in the design/optimization of semiconductor-based quantum information processing schemes. In particular, we focus on interdot exciton-exciton coupling, the key ingredient in recently proposed all-optical quantum processors. Our analysis demonstrates that there is a large window of realistic parameters for which both biexcitonic shift and oscillator strength are compatible with such implementation schemes
Intrinsic electric field effects on few-particle interactions in coupled GaN quantum dots
No full textWe study the multiexciton optical spectrum of vertically coupled GaN/AlN quantum dots with a realistic
three-dimensional direct-diagonalization approach for the description of few-particle Coulomb-correlated states. We present a detailed analysis of the fundamental properties of few-particle/ exciton interactions peculiar of nitride materials. The giant intrinsic electric fields and the high electron/ hole effective masses give rise to different effects compared to GaAs-based quantum dots: intrinsic exciton-exciton coupling, non molecular character of coupled dot exciton wave function, strong dependence of the oscillator strength on the dot height,
large ground-state energy shift for dots separated by different barriers. Some of these effects make GaN/AlN quantum dots interesting candidates in quantum information processing
The C-S Approach for The Management of Median or Paramedian Frontal Sinus Lesion
No full textThe frontal sinus is one the most complex of the paranasal sinuses, its proximity to the cranial vault and the orbit cause that frontal sinus pathologies can progress to involve these structures and lead to significant morbidity, or even death. Surgical management of the frontal sinus is technically challenging, the most commonly used surgical approaches are coronal, butterfly, gullwing and suprabrow. The purpose of this article is to propose the C-S approach, an interesting alternative to the gullwing approach for the managing of median and paramedian frontal sinus lesions or isolated displaced fractures of the anterior wall. The main advantage of this technique is represented by the fact that it follows the new tension lines described in the literature, a curved vertical line that follows the glabellar frown
Central Giant Cell Reparative Granuloma (CGCRG) of the Jaw in Children Treated with Neoadjuvant Bisposphonates: Review and a Case Report
No full textCentral giant cell reparative granuloma (CGCRG) of the jaw is a neoformation localized in the mandible or in the maxillary bone and characterized by fibrous tissue, osteoclast-like giant cells and reactive bone formation. The CGCRG is a less frequent benign tumor but sometimes it is characterized by an aggressive behavior with a very rapid growth. It affects the young adults mainly and the children occasionally. Nowadays no medication therapy is approved for CGCRG in pediatric cases. We present a case of an aggressive form of a mandibular CGCRG in a 5-year child with Arnold-Chiari syndrome. This case is unique for the use of bisphosphonates (BPs) as neoadjuvant therapy in pediatrics. The therapy were administrated with the purpose of arresting the rapid growth of the tumor in order to avoid a demolitive surgery to the young patient. The child was without symptoms and presented an unusual swelling in the left mandible developed in a few weeks. The lesion was diagnosed by a CT scan and it was confirmed by a biopsy performed for histopathological assessment a few days later. The drug therapy consisted of seven cycles iv of Zoledronate associated to Calcium Gluconate. The child was closely observed through clinical and serological evaluations during the following months. About five months after the last cycle of BPs the child underwent CT scan and a conservative surgical treatment, consisted in a deep curettage, was programmed. Seven months after surgery the aesthetic profile of the patient improved and CT scan reported a significant calcic neoapposition in the area of the previous bone lesion. After more than one year from surgery, no relapse was observed. This case report demonstrates that BPs can be used safely in pediatric patients with CGCRG. Especially BPs could have a role as neoadjuvant therapy: If administrated before surgical treatment BPs avoid the necessity of resective surgery and reduce the risk of recurrence in pediatric CGCRG after conservative curettage
Local degradation of selectively oxidized AlGaAs/AlAs distributed Bragg reflectors in lateral-injection vertical-cavity surface-emitting lasers
No full textGaN quantum dot based quantum information/computation processing
No full textIn this paper we propose to use GaN quantum dots (QDs) as building blocks for solid state quantum computing devices. The existence of a strong built-in electric field induced by the spontaneous polarization and by the piezoelectricity is exploited to entangle few-exciton states in coupled QDs without the use of external fields. The analysis of the electro-optical response of the coupled GaN QDs is based on a realistic—i.e. fully tri-dimensional—description of Coulomb-correlated few-electron states, obtained via a direct-diagonalization approach. The combined effect of the built-in electric field and ultrafast sequences of multicolor laser pulses in the few-carrier regime is investigated. We show how the built-in field induces intrinsic dipole-dipole coupling and thus allows the implementation of quantum information processing. As an example we will implement basic quantum information gates and we will demonstrate that our implementation scheme is compatible with a sub-picosecond operation timescale, i.e. with timescales much lower than the decoherence time of the system
Intrinsic dipole-dipole excitonic coupling in GaN quantum dots: application to quantum information processing
No full textWe propose to use GaN quantum dots as building blocks of a solid state quantum bit. The existence of a strong built in electric field induced by the spontaneous polarization and by the piezoelectricity is exploited to entangle the states in coupled quantum dots without external fields. The electro-optical response of the coupled GaN quantum dots is investigated theoretically by means of a realistic description of Coulomb-correlated few-electron states, obtained via a direct-diagonalization approach. We show that the built-in electric field in nitrides induces intrinsic dipole-dipole coupling of the order of some milli-electron-volt and thus allows the implementation of quantum information processing. As an example we will implement the quantum XOR gate. Quantum operations are achieved by a sequence of femtosecond multicolor laser pulses
Low-Frequency Detection in ECG Signals and Joint EEG-Ergospirometric Measurements for Precautionary Diagnosis
No full textHRV (Heart Rate Variability) is an indicator that can be related to different human organs and systems: breathing, heart, brain, pulmonary system, etc. In cardiac clinic, physical exertion can be pre-assessed thanks to HR (Heart Rate) response using appropriate tests to rule out eventual cardiac dysfunction prior to undergo patient to further exams, surgical operations and rehabilitation activities. HR assessment must determine the capability of patient to continue exertion up to a certain level without having angina pain symptoms and brain dysfunctions. The variability of HR is a marker of dynamic load because it is sensitive
and responsive to acute stress. Moreover it is also a marker of a cumulative wear and tear because it declines with advancing age. In this paper we propose combined measurements
of EEG-Ergospirometry and ECG for patient’s cardio-pulmonary condition assessment for allowing doctors to make a decision on rehabilitation or surgical operation for people suspected of suffering from epilepsy seizures. Measurements assessed using frequency domain parameters have permitted the determination of low and high frequencies that are related to sympathetic and parasympathetic activities respectively
Numerical simulations for road tunnels fire safety
No full textAmong the different sections of a road infrastructure, accidents occurred into road tunnels are actually the most effective in terms of victims and damages. European government is facing this dramatic issue through the introduction of Fire Safety Engineering methods and performance based approach in the tunnel safety regulation
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