Spin state dependence of electrical conductivity of spin crossover materials

We studied the spin state dependence of the electrical conductivity of the spin crossover compound [Fe(Htrz)2(trz)](BF4) (Htrz = 1H-1,2,4-triazole) by means of dc electrical measurements. The low spin state is characterized by higher conductance and lower thermal activation energy of the conductivity, when compared to the high spin state

Calorimetric Evidence of Strong-Coupling Multiband Superconductivity in Fe(Te0.57Se0.43) Single Crystal

We have investigated the specific heat of optimally-doped iron chalcogenide superconductor Fe(Te0.57Se0.43) with a high-quality single crystal sample. The electronic specific heat Ce of this sample has been successfully separated from the phonon contribution using the specific heat of a non-superconducting sample (Fe0.90Cu0.10)(Te0.57Se0.43) as a reference. The normal state Sommerfeld coefficient gamma_n of the superconducting sample is found to be ~ 26.6 mJ/mol K^2, indicating intermediate electronic correlation. The temperature dependence of Ce in the superconducting state can be best fitted using a double-gap model with 2Delta_s(0)/kBTc = 3.92 and 2Delta_l(0)/kBTc = 5.84. The large gap magnitudes derived from fitting, as well as the large specific heat jump of Delta_Ce(Tc)/gamma_n*Tc ~ 2.11, indicate strong-coupling superconductivity. Furthermore, the magnetic field dependence of specific heat shows strong evidence for multiband superconductivity

Origin and stability of the dipolar response in a family of tetragonal tungsten bronze relaxors

A new family of relaxor dielectrics with the tetragonal tungsten bronze structure (nominal composition Ba6M3+Nb9O30, M3+ = Ga, Sc or In) were studied using dielectric spectroscopy to probe the dynamic dipole response and correlate this with the crystal structure as determined from powder neutron diffraction. Independent analyses of real and imaginary parts of the complex dielectric function were used to determine characteristic temperature parameters, TVF, and TUDR, respectively. In each composition both these temperatures correlated with the temperature of maximum crystallographic strain, Tc/a determined from diffraction data. The overall behaviour is consistent with dipole freezing and the data indicate that the dipole stability increases with increasing M3+ cation size as a result of increased tetragonality of the unit cell. Crystallographic data suggests that these materials are uniaxial relaxors with the dipole moment predominantly restricted to the B1 cation site in the structure. Possible origins of the relaxor behaviour are discussed.Comment: Main article 32 pages, 8 figures; Supplementary data 24 pages, 4 figure

First experience in off pump coronary artery bypass grafting of anterior descending artery via inferior mini-sternotomy

Spitalul Internaţional “Medpark”, Chişinău, Republica Moldova, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: În prezent pontajul coronarian pe o singură arteră reprezintă o raritate. Cardiologia intervenţională rezolvă marea majoritate a cazurilor cu afectarea patului coronarian cu o singură limitare – afectarea ostială a arterei descendente anterioare (ADA). Pentru pontajul coronarian pe cord bătând (CB): artera toracică internă stângă (ATIS) anastomozată cu ADA, este cunoscut abordul toracic miniminvaziv. Acestui abord îi sunt valabile şi unele exigenţe deosebite: set de ustensile adaptate special pentru minitoracotomie, echipă polidisciplinară bine formată şi, desigur, experienţa chirurgului operator. O problemă actuală, pentru perioada postoperatorie, rămâne combaterea durerii postoperatorii. Scopul lucrării a fost implementarea abordului mini-invaziv în operaţiile pe CB. Material şi metode: Pe parcursul ultimilor 5 ani, operaţi pe CB prin sternotomie inferioară au fost 13 pacienţi (5 femei, 8 bărbaţi), vîrsta medie – 59,3 ani. Toţi pacienţii au prezentat o afectare monovasculară severă pe ADA, segmentul I ostial. Stabilizarea cordului și a arterei – efectuată cu ajutorul dispozitivului “Octopus 4”. Anastomoza ATIS-ADA – efectuată cu sutură Prolene 8/0. Rezultate: Perioada postoperatorie complicată cu hemoragie – 1 pacient, menajată conservativ. Durata medie a spitalizării a constituit 4,5 zile. În perioada precoce şi de lunga durată accese anginoase nu s-au înregistrat. Concluzii: Mini-sternotomia inferioară reprezintă un abord optim către ADA, cu expoziţie suficientă pentru prelevarea ATIS. Sindromul algic postoperator este minim, reconvalescenţa fizică este rapidă, amplituda mişcărilor în membre superioare – nelimitată.Introduction: Nowadays, a single artery bypass surgery is a rarity. Interventional cardiology solves most cases of affected coronary arteries, with a single limitation – ostial involvement of anterior descending coronary artery (ADCA). For beating-heart coronary bypass (BHCB): left internal thoracic artery (LITA) anastomosis with anterior descending artery is well known minimally invasive thoracic approach. But for this approach several special requirements should be met: set of tools specially adapted for mini-thoracotomy, well trained multidisciplinary team and the experience of surgeon. A current problem is combating of the postoperative pain. Aim of the study was the implementation of minimally invasive access in BHCB. Material and methods: During the last five years, 13 patients (5 women, 8 men) with mean age – 59.3 years were operated with BHCB. All patients presented a severe single vessel injury of ADCA in I ostial segment. Stabilization of the heart and artery was carried out with the device Octopus 4. The anastomosis between LITA-ADCA was performed with the Prolene 8/0 suture. Results: The postoperative period was complicated with hemorrhage in 1 patient, treated conservatively. The mean duration of hospitalization was 4.5 days. In early and long-term postoperative period relapses of heart angina were not registered. Conclusion: Lower mini-sternotomy is an optimal approach to ADCA, with sufficient exposition for harvesting LITA. Postoperative pain syndrome is minimal, physical recovering is fast, the amplitude of movements in upper limbs is unrestricted

Elastic and anelastic relaxations accompanying relaxor ferroelectric behaviour of Ba6GaNb9O30 tetragonal tungsten bronze from resonant ultrasound spectroscopy

Tetragonal tungsten bronze (TTB) structures offer some promise as lead-free ferroelectrics and have an advantage of great flexibility in terms of accessible composition ranges due to the number of crystallographic sites available for chemical substitution. The ferroic properties of interest are coupled with strain, which will be important in the context of stability, switching dynamics and thin film properties. Coupling of strain with the ferroelectric order parameter gives rise to changes in elastic properties, and these have been investigated for a ceramic sample of Ba6GaNb9O30 (BGNO) by resonant ultrasound spectroscopy. Room temperature values of the shear and bulk moduli for BGNO are rather higher than for TTBs with related composition which are orthorhombic at room temperature, consistent with suppression of the ferroelectric transition. Instead, a broad, rounded minimum in the shear modulus measured at ~1 MHz is accompanied by a broad rounded maximum in acoustic loss near 115 K and signifies relaxor freezing behaviour. Elastic softening with falling temperature from room temperature, ahead of the freezing interval, is attributed to the development of dynamical polar nanoregions (PNRs), whilst the nonlinear stiffening below ~115 K is consistent with a spectrum of relaxation times for freezing of the PNR microstructure

Highly enriched Betaproteobacteria growing anaerobically with p-xylene and nitrate

The identity of the microorganisms capable of anaerobic p-xylene degradation under denitrifying conditions is hitherto unknown. Here, we report highly enriched cultures of freshwater denitrifying bacteria that grow anaerobically with p-xylene as the sole organic carbon source and electron donor. Long curved rods, with 95% 16S rRNA gene sequence identity to Denitratisoma oestradiolicum, dominated the enrichment cultures (>91% of all cells), as detected by phylotype-specific probes. These Rhodocyclaceae microorganisms were distantly related to other denitrifying hydrocarbon-degrading Betaproteobacteria from the Azoarcus-Thauera clade. Complete oxidation p-xylene to CO(2) coupled to denitrification was suggested by quantitative measurements of substrate consumption. Metabolite analysis identified (4-methylbenzyl)succinate and (4-methylphenyl)itaconate, suggesting addition to fumarate as an initial activation reaction