Synthesis,characterization and photovoltaic properties of phase pure Cu<Subscript>2</Subscript>SnSe<Subscript>3</Subscript> nanostructures using molecular precursors

Phase pure Cu₂SnSe₃ (CTSe) nanostructures have been synthesized using metal selenolates, [Me₂Sn{SeC₅H₃(Me-3)N}₂] (molecular structure of [Me₂Sn{SeC₅H₃(Me-3)N}₂] has been established by single crystal X-ray analysis) and [Cu{SeC₅H₃(Me-3)N}]₄ as molecular precursors in oleylamine (OLA) and tri-n-octylphosphine oxide (TOPO). The effect of temperature on final composition of nanostructures has also been investigated. Powder X-ray diffraction, Raman and X-ray photoelectron spectroscopy (XPS) were used to investigate the crystal structure, phase purity and homogeneity of the nanostructures while the electron microscopy revealed the morphology of the nanostructures. Superconducting quantum interference device (SQUID) measurements of CTSe nanostructures showed weak magnetic ordering at low temperature (below 50 K) attributed to the presence of some defect centres in the sample. The CTSe nanostructure possess an optical band gap of 1.7 eV deduced from diffuse reflectance spectroscopy (DRS) and showed photo response which makes them promising candidate for alternative low cost photon absorber material.     

Targeting HGF/c-MET Axis in Pancreatic Cancer

Pancreatic cancer (pancreatic ductal adenocarcinoma (PDAC/PC)) has been an aggressive disease that is associated with early metastases. It is characterized by dense and collagenous desmoplasia/stroma, predominantly produced by pancreatic stellate cells (PSCs). PSCs interact with cancer cells as well as other stromal cells, facilitating disease progression. A candidate growth factor pathway that may mediate this interaction is the hepatocyte growth factor (HGF)/c-MET pathway. HGF is produced by PSCs and its receptor c-MET is expressed on pancreatic cancer cells and endothelial cells. The current review discusses the role of the MET/HGF axis in tumour progression and dissemination of pancreatic cancer. Therapeutic approaches that were developed targeting either the ligand (HGF) or the receptor (c-MET) have not been shown to translate well into clinical settings. We discuss a two-pronged approach of targeting both the components of this pathway to interrupt the stromal–tumour interactions, which may represent a potential therapeutic strategy to improve outcomes in PC.     

Mapping of two mouse membrane-type matrix metalloproteinase (MT-MMP) genes, Mmp15 and Mmp16, to mouse chromosomes 8 and 4, respectively

OBJECTIVE: The primary purpose of this study was to compare the reliability of differing sets of criteria for attachment disorders by using a retrospective case review. METHOD: Forty-eight consecutive clinical case summaries from an infant behavior clinic were reviewed by four experienced clinicians. Attachment disorders were coded as present or absent by using competing criteria and were scored by using a continuous scale of relationship functioning. RESULTS: The reliability of alternative criteria was acceptable, but the reliability of DSM-IV criteria in diagnosing attachment disorders was marginal. Preliminary validity for the criteria was demonstrated by the fact that more severe relationship disturbances were seen in infants diagnosed with attachment disorders than in infants diagnosed with other disorders. CONCLUSIONS: Standardized assessments of at-risk populations should be used to replicate these preliminary results; revision of DSM-IV criteria may be necessary to obtain adequate reliability for diagnosing attachment disorders.     

Oxygen incorporation duringin situ growth of YBCO films on both sides of substrates

Oxygen out-diffusion during cooling and heating ofin situ grown {ie685-1} (YBCO) films in low oxygen pressure used during growth by pulsed laser deposition was studied in the temperature range 700−450°C usingin situ resistance measurements. Results indicate that irrespective of the number of cooling and heating cycles seen by the films, full oxygenation of the films can be realized by the final cooling from the growth temperature in 500 torr oxygen pressure. This result has been successfully used to sequentially grow high quality YBCO films on both sides of LaAlO₃ substrates. These films have been used for the fabrication of X-band microstrip resonators with superconducting ground plane.     

Correlation of trap generation to charge-to-breakdown (Qbd): a physical-damage model of dielectric breakdown

Ultrathin gate and tunnel oxides in MOS devices are subjected to high-field stress during device operation, which degrades the oxide and eventually causes dielectric breakdown. Oxide reliability, therefore, is a key concern in technology scaling for ultra-large scale integration (ULSI). Here we provide critical new insight into oxide degradation (and consequently, reliability) by a systematic study of five technologically relevant parameters, namely, stress-current density, oxide thickness, stress temperature, charge-injection polarity (gate versus substrate), and nitridation of pure oxide. For all five parameters, a strong correlation has been observed between oxide degradation and the generation of new traps (distinct from the filling of intrinsic traps). Further, we observe that this correlation is independent of the trap polarity (positive versus negative). Based on this correlation, and based on the fundamental link between electronic properties and atomic structure, a physical-damage model of dielectric breakdown has been proposed. The concept of the physical-damage model is that the oxide suffers dielectric breakdown when physical damage due to broken bonds forms a defect-filled filamentary path in the oxide, that conducts excessive current. A good monitor of this physical damage is trap generation, which we believe is caused by physical bond breaking in the oxide and at the interface. The model has been quantified empirically by the correlation between trap generation and Q_bd     

Comparative toxicity of nanoparticulate ZnO, bulk ZnO, and ZnCl2 to a freshwater microalga (Pseudokirchneriella subcapitata): the importance of particle solubility

Metal oxide nanoparticles are finding increasing application in various commercial products, leading to concerns for their environmental fate and potential toxicity. It is generally assumed that nanoparticles will persist as small particles in aquatic systems and that their bioavailability could be significantly greater than that of larger particles. The current study using nanoparticulate ZnO (ca. 30 nm) has shown that this is not always so. Particle characterization using transmission electron microscopy and dynamic light scattering techniques showed that particle aggregation is significant in a freshwater system, resulting in flocs ranging from several hundred nanometers to several microns. Chemical investigations using equilibrium dialysis demonstrated rapid dissolution of ZnO nanoparticles in a freshwater medium (pH 7.6), with a saturation solubility in the milligram per liter range, similar to that of bulk ZnO. Toxicity experiments using the freshwater alga Pseudokirchneriella subcapitata revealed comparable toxicity for nanoparticulate ZnO, bulk ZnO, and ZnCl2, with a 72-h IC50 value near 60 microg Zn/ L, attributable solely to dissolved zinc. Care therefore needs to be taken in toxicity testing in ascribing toxicity to nanoparticles per se when the effects may be related, at least in part, to simple solubility.     

Nanocontact Tailoring via Microlensing Enables Giant Postfabrication Mesoscopic Tuning in a Self‐Assembled Ultrasonic Metamaterial

The ability to tune the resonant frequency of a self‐assembled ultrasonic metamaterial with mesoscale spatial resolution, after fabrication, by up to 250% is demonstrated. This tunability is achieved by the microlensing‐enabled modification of nanocontact features, wherein the metamaterial resonant elements “dig in” to the substrate. In addition to tunability exceeding prior MHz–GHz frequency ultrasonic metamaterial examples, the system presented herein can be tuned after assembly at a spatial resolution commensurate with the laser spot's diameter. It is posited that these aforementioned advantages will enable a new class of ultrasonic gradient index devices, such as ultrasonic elastic wave cloaks, that can be manufactured in a scalable manner and then rapidly tuned. Finally, it is expected that this large tunability at ultrasonic frequencies will have broader application to areas including optomechanics, acoustoplasmonics, quantum‐mechanical oscillators, and adhesion control.     

能源效率:半导体21世纪的挑战

全球能源需求量的增长率已经远远高于传统能源的供应,但是,半导体行业能够帮助改善能源生产、输送以及消耗环节的效率。从远古时代开始,能源就已经成为文明进步的主要推动力。     

A group-theoretic analysis of symmetric target scattering with application to landmine detection

Landmines are generally constructed such that they possess a high level of geometric symmetry and are then buried in a manner that preserves this symmetry. The scattered response of such a symmetric target will likewise exhibit the symmetry of the target, as well as the electromagnetic reciprocity exhibited by all scatterers. Group theory provides a mathematic tool for describing geometric symmetry, and it can likewise be used to describe the symmetries inherent in the bistatic scattering from mines. Specifically, group theory can be used to determine specific forms of the dyadic Green's function of symmetric scatterers, such that multiple scattering solutions can be determined from a knowledge of a single bistatic geometry. Likewise, group theory can be used both to determine and analyze degenerate cases, wherein specific bistatic responses can be identified as zero regardless of target size, shape, or material. These results suggest a method for classifying subsurface targets as either symmetric or asymmetric. From the group-theoretic analysis, scattering features can be constructed that are indicative of target symmetry, but invariant with respect to other target parameters such as size, shape, or material. These features provide a physically based, target-independent value to aid in mine detection and/or clutter rejection. To test the efficacy of this idea, an extensive collection of bistatic ground-penetrating radar (GPR) measurements was taken for both a symmetric and an asymmetric target. The two targets were easily discernable using symmetry features only, a result that suggests symmetry features can be effective in identifying subsurface targets.