Optical refrigeration with coupled quantum wells

Refrigeration of a solid-state system with light has potential applications for cooling small-scale electronics and photonics. We show theoretically that two coupled semiconductor quantum wells are efficient cooling media for optical refrigeration because they support long-lived indirect electron-hole pairs. Thermal excitation of these pairs to distinct higher-energy states with faster radiative recombination allows an efficient escape channel to remove thermal energy from the system. This allows reaching much higher cooling efficiencies than with single quantum wells. From band-diagram calculations along with an experimentally realistic level scheme we calculate the cooling efficiency and cooling yield of different devices with coupled quantum wells embedded in a suspended nanomembrane. The dimension and composition of the quantum wells allow optimizing either of these quantities, which cannot, however, be maximized simultaneously. Quantum-well structures with electrical control allow tunability of carrier lifetimes and energy levels so that the cooling efficiency can be optimized over time as the thermal population decreases due to the cooling.Comment: 10 pages, 5 figure

Unraveling the mesoscopic character of quantum dots in nanophotonics

We provide a microscopic theory for semiconductor quantum dots that explains the pronounced deviations from the prevalent point-dipole description that were recently observed in spectroscopic experiments on quantum dots in photonic nanostructures. At the microscopic level the deviations originate from structural inhomogeneities generating a large circular quantum current density that flows inside the quantum dot over mesoscopic length scales. The model is supported by the experimental data, where a strong variation of the multipolar moments across the emission spectrum of quantum dots is observed. Our work enriches the physical understanding of quantum dots and is of significance for the fields of nanophotonics, quantum photonics, and quantum-information science, where quantum dots are actively employed.Comment: 6 pages, 5 figure

Probing electric and magnetic vacuum fluctuations with quantum dots

The electromagnetic-vacuum-field fluctuations are intimately linked to the process of spontaneous emission of light. Atomic emitters cannot probe electric- and magnetic-field fluctuations simultaneously because electric and magnetic transitions correspond to different selection rules. In this paper we show that semiconductor quantum dots are fundamentally different and are capable of mediating electric-dipole, magnetic-dipole, and electric-quadrupole transitions on a single electronic resonance. As a consequence, quantum dots can probe electric and magnetic fields simultaneously and can thus be applied for sensing the electromagnetic environment of complex photonic nanostructures. Our study opens the prospect of interfacing quantum dots with optical metamaterials for tailoring the electric and magnetic light-matter interaction at the single-emitter level.Comment: 6 pages, 4 figure

Bolile inflamatorii intestinale la copii în contextul clasificării Paris, 2010

L’Institut de la mère et de l’enfant. Département de gastroentérologie pédiatrique. IMSP IMetEBackground. Diagnosis of inflammatory bowel diseases (IBD), including subtypes of ulcerative colitis, Crohn's disease and unspecified colitis remains uncertain, but according to several international guidelines, diagnosis is based on clinical manifestations, endoscopic examination, and histologic evaluation of bowel mucosa. The onset and evolution of inflammatory bowel diseases in children are highlighted by several atypical phenotypes, thus the Paris classification, 2010 clearly defines the subtypes of inflammatory bowel disease, pointing out the diagnosis shortcomings ensuring correct diagnosis, phenotypic evolution, but also prognosis which allows a personalized and rational therapeutic conduct. Purpose. To evaluate the evolutionary phenotypic features of inflammatory bowel diseases, Crohn’s disease, and ulcerative colitis in children in the Republic of Moldova in comparison with other European centers, in the context of the Paris classification, 2010. Material and methods. The research was based on a prospective study, which included all patients hospitalized in the Department of Gastroenterology, PMSI Mother and Child Institute, during 2010 and 2014, with the diagnosis of UC or CD, established as a result of history taking, clinical examination, laboratory tests, endoscopic and histological examination, stratified according to the Paris classification, 2010. Results. There were included 51 children with inflammatory bowel diseases in our study. Of them, 45 (88.23%) with ulcerative colitis and 6 (11.76%) with Crohn’s disease, aged between 4 months and 17 years. Patients with Crohn’s disease, by criterion A (age), 4 (66.67%) children were included in criterion A1a and 2 (33.34%) children in criterion A1b, data similar to other European centers, being predominant in children older than 10 years. Colonic location was estimated at 66.67% (4/6) (L2), while the ileocolonic location in 33.34% (2/6), as other regions without a certain location dominant as a whole. Crohn`s disease pattern in all national children is non-stenosing and non-penetrating (B1), is characterized by lack of perineal damage. Stature-weight retardation accounted for 83.34% of cases. Children with ulcerative colitis in the Republic of Moldova are characterized by the same process extension, pancolitis being the most common (E4 - proximal to the hepatic flexure) in 64.45% of cases, left colitis (E2 - distal to the splenic flexure) in 24.39% of cases, and extensive colitis (E3 - distal to the hepatic flexure) 8.9% of cases, and finally proctitis (E1) in 4.45% of cases. The severity rate assessed according to pediatric activity index (PUCAI) was estimated in 82.3% of cases. Conclusions. According to the Paris classification, 2010, Crohn’s disease, in children in the Republic of Moldova, is characterized by criteria similar to other European centers, such as age (A1a, A1b), location (L), retardation (G), but it is marked by a non-stenosing and non-penetrating (B1) pattern, as well as cases of ulcerative colitis do not diverge from other European centers, localization criterion (E), while the severity of the disease is noticeable especially in national children.Background. Diagnosticul bolilor inflamatorii intestinale (BII), ce include subtipurile colita ulceroasă, boala Crohn şi colita neprecizată, rămîne a fi incert, însă conform mai multor ghiduri internaţionale diagnosticul este bazat pe manifestările clinice, examenul endoscopic şi evaluarea histologică a mucoasei intestinului. Debutul şi evoluţia bolilor inflamatorii intestinale la copii şi adolescenţi se evidenţiază prin mai multe fenotipuri atipice, astfel clasificarea Paris, 2010 defineşte în mod cert subtipurile de boală inflamatorie intestinală, evidenţiază lacunele de diagnostic asigurînd stabilirea unui diagnostic corect, evoluţia fenotipică, dar şi pronosticul, ceea ce permite o conduită terapeutică personalizată raţional. Scopul. Evaluarea particularităţilor fenotipice evolutive ale maladiilor inflamatorii intestinale, boala Crohn şi colita ulceroasă, a copiilor din Republica Moldova în comparaţie cu alte centre europene, în contextul clasificării Paris, 2010. Material and methods. Cercetarea a fost fundamentată pe un studiu prospectiv, ce-a inclus toţi pacienţii internaţi în secţia gastroenterologie a IMSP Institutul Mamei şi Copilului în perioada 2010–2014, cu diagnosticul de CU sau BC, stabilit în rezultatul anamnezei, examenului clinic, testelor de laborator, examenului endoscopic şi histologic şi stratificaţi conform clasificării Paris, 2010. Results. În studiul nostru au fost incluşi 51 copii cu maladii inflamatorii intestinale, dintre care 45 (88,23%) cu colită ulceroasă şi 6 (11,76%) cu boala Crohn, cu vîrsta cuprinsă între 4 luni şi 17 ani. Pacienţii cu boala Crohn, după criteriul A (vîrsta), 4 (66,67%) copii s-au inclus în criteriul A1a şi 2 (33,34%) copii în criteriul A1b, date similare cu alte centre europene, predominînd copii mai mari de 10 ani. În 66,67% (4/6) s-a estimat localizare colonică (L2) şi în 33,34% (2/6) iliocolonică, la fel altor regiuni, fără o anumită dominantă de localizare per ansamblu. Patternul bolii Crohn la toţi copii naţionali este nonstenozant, non-penetrant (B1) şi se caracterizează prin lipsa afectării perianale, iar retardul staturo-ponderal a fost prezent în 83,34% cazuri. Copii cu colită ulceroasă, din Republica Moldova, se caracterizează prin aceeaşi extindere a procesului, cel mai frecvent evidenţiindu-se pancolita (E4 – proximal de flexura hepatică) în 64,45% cazuri, urmează colita de stînga (E2 – distal de flexura splenică) în 24,39% cazuri, apoi colita extensivă (E3 – distal de flexura hepatică) 8,9% cazuri şi la final proctita (E1) cu 4,45% cazuri. Gradul de severitate evaluat conform indicelui pediatric de activitate (PUCAI), a fost estimat în 82,3% cazuri. Conclusions. La copii din Republica Moldova, conform clasificării Paris, 2010, boala Crohn, se remarcă prin criterii similare altor centre europene, cum ar fi vîrsta (A1a, A1b), localizarea (L), retardul (G), dar se evidenţiază prin patternul non-stenozant, non-penetrant (B1), la fel şi cazurile de colita ulceroasă nu prezintă divergenţe între alte centre europene, la criteriul localizare (E), pe cînd severitatea maladiei este remarcată, în special la copii naţionali

Воспалительные заболевания кишечника в Pеспублике Mолдова в рамках Eвропейской Oрганизации по изучению болезни Kрона и язвенного колита – EpiCom-ECCO

IMSP Institutul Mamei şi CopiluluiПредпосылка/Справочная информация: Заболеваемость воспалительными заболеваниями кишечника, болезнью Крона и язвенным колитом подлежит значительному изменению во всем мире, болезнь Крона приходится на долю населения от 0 и 24,3/100 000, и, соответственно, язвенный колит на долю населения от 0 и 20,2/100 000, с уменьшением в промышленных зонах. Материалы и методы: с целью определения географического распространения язвенного колита и болезни Крона в Европе, включая Республику Молдова, был разработан единый акт/протокол – Совместное европейское изучение воспалительного заболевания кишечника – EC IBD, которым руководствовалось 20 европейских центров. В Республике Молдова существовало 2 центра для детей: ПМСУ Институт Матери и Ребенка, Отделение гастроэнтерологии, и для взрослого населения: Республиканская Клиническая Больница, Клиника гастроэнтерологии. Результаты: на европейском уровне Республика Молдова находится с уровнем заболеваемости от 2,9 на 100 тысяч населения, для детского населения, и для взрослого населения 4,3 на 100 тысяч населения, что определяет/квалифицирует с меньшей заболеваемостью в Восточной Европе. В обеих группах пациентов (детей/взрослых) заболеваемость была высокой в Западной Европе от 6,9 на 100000 детского населения, и, соответственно, от 18,5 на 100 000 взрослого населения, еще раз подтвердив, влияние факторов окружающей среды на этиопатогенез воспалительного заболевания кишечника. Выводы: Республика Молдова является регионом с малой заболеваемостью (2,9-4,3 на 100 тысяч населения) воспалительными заболеваниями кишечника, хотя национальные данные отмечают тенденцию роста.Introducere. Incidenţa bolilor inflamatorii intestinale, boala Crohn şi colita ulceroasă, este supusă unor variaţii considerabile în întreaga lume, fluctuînd între 0 şi 24,3/100 000 de locuitori pentru boala Crohn, şi respectiv 0 şi 20,2/100 000 de locuitori, pentru colita ulceroasă, cu precădere în ţările industrializate. Material şi metode: În scopul aprecierii distribuţiei geografice a colitei ulceroase şi bolii Crohn în Europa, inclusiv Republica Moldova a fost elaborat protocolul unic – European Cooperative Study of Inflammatory Bowel Disease – EC IBD, de care s-au condus 20 de centre europene. În Republica Moldova au existat 2 centre, pentru populaţia pediatrică, IMSP Institutul Mamei şi Copilului, Departamentul de gastroenterology şi pentru populaţia adultă, Spitalul Clinic Republican, Clinica Gastroenterologie. Rezultate: La nivel european, Republica Moldova se plasează cu o incidenţă de 2,9 la 100 mii populaţie, pentru populaţia pediatrică şi 4,3 la 100 mii populaţie, pentru populaţia adultă, ce o califi că printre regiunile cu incidenţă mică din Europa de Est. În ambele loturi de pacienţi, copii/adulţi, incidenţa cea mai mare a fost în Europa de Vest 6,9 la 100 mii populaţie pediatrică şi respective 18,5 la 100 mii populaţie adultă, confi rmînd încă o dată impactul factorilor de mediu în etiopatogenia bolilor infl amatorii intestinale. Concluzii: Republica Moldova este o regiune cu incidenţă mică (2,9 - 4,3 la 100 mii populaţie) a maladiilor inflamatorii intestinale, deşi datele naţionale remarcă un trend în ascensiune

Decay dynamics and exciton localization in large GaAs quantum dots grown by droplet epitaxy

We investigate the optical emission and decay dynamics of excitons confined in large strain-free GaAs quantum dots grown by droplet epitaxy. From time-resolved measurements combined with a theoretical model we show that droplet-epitaxy quantum dots have a quantum efficiency of about 75% and an oscillator strength between 8 and 10. The quantum dots are found to be fully described by a model for strongly-confined excitons, in contrast to the theoretical prediction that excitons in large quantum dots exhibit the so-called giant oscillator strength. We attribute these findings to localized ground-state excitons in potential minima created by material intermixing during growth. We provide further evidence for the strong-confinement regime of excitons by extracting the size of electron and hole wavefunctions from the phonon-broadened photoluminescence spectra. Furthermore, we explore the temperature dependence of the decay dynamics and, for some quantum dots, observe a pronounced reduction in the effective transition strength with temperature. We quantify and explain these effects as being an intrinsic property of large quantum dots owing to thermal excitation of the ground-state exciton. Our results provide a detailed understanding of the optical properties of large quantum dots in general, and of quantum dots grown by droplet epitaxy in particular.Comment: 13 pages, 7 figure

Reinforcement Learning with Neural Networks for Quantum Feedback

Machine learning with artificial neural networks is revolutionizing science. The most advanced challenges require discovering answers autonomously. This is the domain of reinforcement learning, where control strategies are improved according to a reward function. The power of neural-network-based reinforcement learning has been highlighted by spectacular recent successes, such as playing Go, but its benefits for physics are yet to be demonstrated. Here, we show how a network-based "agent" can discover complete quantum-error-correction strategies, protecting a collection of qubits against noise. These strategies require feedback adapted to measurement outcomes. Finding them from scratch, without human guidance, tailored to different hardware resources, is a formidable challenge due to the combinatorially large search space. To solve this, we develop two ideas: two-stage learning with teacher/student networks and a reward quantifying the capability to recover the quantum information stored in a multi-qubit system. Beyond its immediate impact on quantum computation, our work more generally demonstrates the promise of neural-network-based reinforcement learning in physics.Comment: 7 pages maintext + methods + supplementary, 6 maintext figures; for related lectures, see: http://machine-learning-for-physicists.or

Sindromul Alagille la copil: protocol clinic naţional PCN-259

IMSP Institutul Mamei şi CopiluluiProtocolul naţional a fost elaborat de către grupul de lucru al Ministerului Sănătăţii al Republicii Moldova (MS RM), constituit din specialiştii IMSP Institutul Mamei şi Copilului. Protocolul de faţă a fost fundamentat în conformitate cu ghidurile internaţionale actuale privind „Sindromul Alagille la copil” şi va servi drept matrice pentru elaborarea protocoalelor instituţionale. La recomandarea MS RM pentru monitorizarea protocoalelor instituţionale pot fi folosite formulare suplimentare, care nu sunt incluse în protocolul clinic naţional

Vitamin D (Vit.D) and diseases associated with its metabolism

State University of Medicine and Pharmacy „Nicolae Testemiţanu”, Catedra de biochimie și biochimie clinică, Chisinau, Republic of Moldova, Congresul consacrat aniversării a 75-a de la fondarea Universității de Stat de Medicină și Farmacie „Nicolae Testemițanu” din Republica Moldova, Ziua internațională a științei pentru pace și dezvoltareIntroduction: Vit.D receptor (VDR) and the enzymes that metabolize this vitamin have an impact, not only on the homeostasis of calcium and phosphate, but also on other tissues. This allows the possibility to discover new aspects of metabolism and clinical implications of vitamin. Purpose: To analyze and synthesize modern data from the literature on the pleiotropic effects of vitamin D, the importance, causes, mechanism and consequences of its metabolism defects to identify new diagnostic and therapeutic strategies. Material and methods: Recent data on international scientific literature were analyzed, especially in the PubMed and PubMed Central online library. Results: Vitamin D participates in a lot of processes due to VDR and RXR receptors that are found in different tissues. The enzymes and genes that encode them like CYP2R1, CYP27B1, CYP24A1, etc, play an important role in the development of these processes. The disturbance of the metabolism enzymes enhances the correlation between Vit.D and a number of diseases such as: prostate, breast, colorectal cancer, diabetes etc. Conclusions: The enzymes and genes involved in the metabolism of the vitamin and its action have effects on different cells. Treatment and supplementations with Vit.D, with variable dose, starting 400 U/l attenuates the manifestations of symptoms as well as the risk of developing other diseases

Correlation between the superior, anterior and inferior occlusal plane with TMJ dysfunctions

Rezumat Studiul a urmărit determinarea corelaţiei dintre diferite clase scheletice, deplasarea condilară și înclinarea planurilor ocluzale superior posterior și superior anterior. Sistemul stomatognat este unul complex în dezvoltarea sa filo– și ontogenetică, funcţionalitatea acestuia fiind influenţată de diverși factori. Sindroamele de disfuncţie a articulaţiei temporomandibulare pot avea forme clinice miogene, artrogene, tulburări de dezvoltarea, hipomobilitate cronică. Asupra funcţionalităţii un impact deosebit îl au o serie de parametri, printre care planul ocluzal și tipul de clasa scheletică. În populaţia europeană, se atestă o tendinţă de predominare a clasei scheletice II, care e un factor predispozant și favorizant pentru apariţia disfuncţiei temporomandibulare. Studiul nostru a relevat că majoritatea pacienţilor cu această clasă scheletică prezintă deplasare condiliană. Determinarea valorilor planului ocluzal are o importanţă deosebită în evalurea diagnostică a pacientului și în stabilirea complexităţii tratamentului.Abstract The study aimed to determine the correlation between different skeletal classes, the condylar displacement and the inclination of the superior posterior and superior anterior occlusal planes. The stomatognathic system is a complex one in its phylogenetic and ontogenetic development, its functionality being influenced by various factors. Temporomandibular joint dysfunction syndromes may present as the following clinical forms: myogenous, arthrogenous, developmental disorders, chronic hypomobility. On the functionality of the system, a special impact has a number of parameters, including the occlusal plane and the type of the skeletal class. In the European population, there is a tendency of predomination for the skeletal class II, which is a predisposing and favorable factor for the appearance of temporomandibular disorders. Our study revealed that the majority of patients with this skeletal class have a condylar displacement. Determining the values of the occlusal plane is of particular importance in the diagnostic evaluation of the patient and in establishing the complexity of the treatment