A large thermoelectric power factor in heavily boron-doped p-type nanograined Si with grain sizes ∼30 nm and grain boundary regions of ∼2 nm is reported. The reported power factor is ∼5 times higher than in bulk Si. It originates from the surprising observation that for a specific range of carrier concentrations, the electrical conductivity and Seebeck coefficient increase simultaneously. The two essential ingredients for this observation are nanocrystallinity and extremely high boron doping levels. This experimental finding is interpreted within a theoretical model that considers both electron and phonon transport within the semiclassical Boltzmann approach. It is shown that transport takes place through two phases so that high conductivity is achieved in the grains, and high Seebeck coefficient by the grain boundaries. This together with the drastic reduction in the thermal conductivity due to boundary scattering could lead to a significant increase of the figure of merit ZT. This is one of the rare observations of a simultaneous increase in the electrical conductivity and Seebeck coefficient, resulting in enhanced thermoelectric power factor.

In our experimental model, bone marrow-derived mesenchymal stem cells injection improved muscle regeneration and increased contractile function of anal sphincters after injury and repair. Therefore, mesenchymal stem cells may represent an attractive tool for treating anal sphincter lesions in humans. Investigations into the biologic basis of this phenomenon should increase our knowledge on underlying mechanisms involved in sphincter repair.

We performed a systematic review of epidemiological, diagnostic, and therapeutic outcomes of esophageal perforations. A systematic review was performed in PubMed database using the key-phrase 'esophageal perforation'. All studies regarding acute esophageal perforations were reviewed and parameters of epidemiology, diagnosis, and management published in the literature from 2005 up to 2015 were included in the study. Studies of postoperative esophageal leaks were excluded. Two researchers performed individually the research, while quality assessment was performed according to GRADE classification. Main outcomes and exposure were overall mortality, perforation-to-admission interval, anatomical position, cause, prevalent symptom at admission, diagnostic tests used, type of initial management (conservative or surgery), healing rate, and fistula complication. There were 1319 articles retrieved, of which 52 studies including 2,830 cases finally met inclusion criteria. Mean duration of study period was 15.2 years. Mean patient age was 58.4 years. Out of 52 studies included, there were 43 studies of very low or low quality included. The overall mortality rate according to extracted data was 13.3% (n = 214, 1,644 patients, 39 studies). Admission before 24 hours was reported in 58.1% of patients (n = 514). Position was thoracic in 72.6% of patients (n = 813, 1,120 patients, 20 studies). Mean cause of perforation was iatrogenic in 46.5% of patients (n = 899, 1,933 patients, 40 studies). Initial management was conservative in 51.3% of cases (n = 904, 1,762 patients, 41 studies) CT confirmed diagnosis in 38.7% of overall cases in which it was used as imaging diagnostic procedure (n = 266), X-ray in 36.6% (n = 231), and endoscopy in 37.4% (n = 343). Sepsis on admission was observed in 23.3% of cases (209 out of 898 patients, 16 studies). The present systematic review highlighted the significant proportion of cases diagnosed with delay over 24 hours, mortality rates ranging over 10% and no consensus regarding optimal therapeutic approach and optimal diagnostic management. As esophageal perforation represents a high-risk clinical condition without consensus regarding optimal management, there should be large multicenter prospective studies or Randomized Controlled Trial (RCT)s performed in order to advance diagnostic and therapeutic approach of such challenging pathology.

In this work, we describe a novel idea that allows for high thermoelectric power factors in two-phase materials that are heavily doped with an inhomogeneous distribution of dopants. We show that a concurrent increase of the electrical conductivity and Seebeck coefficient and a consequent increase of the power factor can be achieved in such systems. To explain the concept, we employ a semiclassical one-dimensional model that considers both electron and phonon transport through a series connection of two-phases of the material. We discuss microscopic characteristics of the material and the formation of the two phases (grains and grain boundaries in our case) by the inhomogeneous distribution of dopants in the polycrystalline material. Our theoretical investigation reveals that: (1) the improvement in the Seebeck coefficient can be attributed to carrier filtering due to the energy barriers at the grain boundaries, and to the difference in the lattice thermal conductivity of the grains and grain boundaries, and (2) the improvement in the electrical conductivity is a result of a high Fermi level in the grains. This allows high energy carriers to contribute to transport, which increases the impurity scattering limited mean-free-path, and increases the conductivity in the grains and thus in the whole material. Such an unexpected concurrent increase of the electrical conductivity and the Seebeck coefficient was recently observed in heavily boron-doped polycrystalline silicon of grain sizes <100 nm in which a silicon-boride phase is formed around the grain boundaries. We provide a simple 1D model that explains the behavior of this system, indicating processes that can take place in heavily doped nanocrystalline materials