Spatial distribution of local density of states in vicinity of impurity on semiconductor surface

We present the results of detailed theoretical investigations of changes in local density of total electronic surface states in 2D anisotropic atomic semiconductor lattice in vicinity of impurity atom for a wide range of applied bias voltage. We have found that taking into account changes in density of continuous spectrum states leads to the formation of a downfall at the particular value of applied voltage when we are interested in the density of states above the impurity atom or even to a series of downfalls for the fixed value of the distance from the impurity. The behaviour of local density of states with increasing of the distance from impurity along the chain differs from behaviour in the direction perpendicular to the chain.Comment: 6 pages, 5 figure

Lead‐Free Semiconductors: Soft Chemistry, Dimensionality Control, and Manganese‐Doping of Germanium Halide Perovskites

Lead halide perovskites have drawn enormous interest due to their exceptional photovoltaic and optoelectronic properties. However, the heavy metal lead is harmful to humans and the environment resulting in a need for strategies to replace this toxic element. Herein, we report a facile aqueous synthesis of CsGeX3 (X=I, Br) perovskite nanocrystals with size control achieved by varying the concentration of a cysteammonium halide ligand. We observe a variety of morphologies including pyramidal, hexagonal, and spheroidal. CsGeX3 nanocrystals undergo a lattice expansion due to partial replacement of Cs+ with larger cysteNH3+ cations into their lattice. We successfully dope Mn2+into the CsGeX3 lattice for the first time with incorporation of up to 29% in bulk and 16% in nano samples. XRD peak shifts and EPR hyperfine splitting strongly indicate that Mn2+ is doped into the lattice. Our results introduce a new member to the lead‐free halide perovskite family and set the fundamental stage for their use in optoelectronic devices

Can a total knee arthroplasty be both rotationally unconstrained and anteroposteriorly stabilised? A pulsed fluoroscopic investigation

Objectives: Throughout the 20th Century, it has been postulated that the knee moves on the basis of a four-bar link mechanism composed of the cruciate ligaments, the femur and the tibia. As a consequence, the femur has been thought to roll back with flexion, and total knee arthroplasty (TKA) prostheses have been designed on this basis. Recent work, however, has proposed that at a position of between 0° and 120° the medial femoral condyle does not move anteroposteriorly whereas the lateral femoral condyle tends, but is not obliged, to roll back - a combination of movements which equates to tibial internal/femoral external rotation with flexion. The aim of this paper was to assess if the articular geometry of the GMK Sphere TKA could recreate the natural knee movements in situ/in vivo. Methods: The pattern of knee movement was studied in 15 patients (six male: nine female; one male with bilateral TKAs) with 16 GMK Sphere implants, at a mean age of 66 years (53 to 76) with a mean BMI of 30 kg/m2 (20 to 35). The motions of all 16 knees were observed using pulsed fluoroscopy during a number of weight-bearing and non-weight-bearing static and dynamic activities. Results: During maximally flexed kneeling and lunging activities, the mean tibial internal rotation was 8° (standard deviation (SD) 6). At a mean 112° flexion (SD 16) during lunging, the medial and lateral condyles were a mean of 2 mm (SD 3) and 8 mm (SD 4) posterior to a transverse line passing through the centre of the medial tibial concavity. With a mean flexion of 117° (SD 14) during kneeling, the medial and lateral condyles were a mean of 1 mm (SD 4) anterior and 6 mm (SD 4) posterior to the same line. During dynamic stair and pivoting activities, there was a mean anteroposterior translation of 0 mm to 2 mm of the medial femoral condyle. Backward lateral condylar translation occurred and was linearly related to tibial rotation. Conclusion: The GMK Sphere TKA in our study group shows movements similar in pattern, although reduced in magnitude, to those in recent reports relating to normal knees during several activities. Specifically, little or no translation of the medial femoral condyle was observed during flexion, but there was posterior roll-back of the lateral femoral condyle, equating to tibiofemoral rotation. We conclude that the GMK Sphere is anteroposteriorly stable medially and permits rotation about the medial compartment

One-Dimensional Energy Dispersion of Single-Walled Carbon Nanotubes by Resonant Electron Scattering

We characterized the energy band dispersion near the Fermi level in single-walled carbon nanotubes using low-temperature scanning tunneling microscopy. Analysis of energy dependent standing wave oscillations, which result from quantum interference of electrons resonantly scattered by defects, yield a linear energy dispersion near EF, and indicate the importance of parity in scattering for armchair single-walled carbon nanotubes. Additionally, these data provide values of the tight-binding overlap integral and Fermi wavevector in good agreement with previous work, but indicate that the electron coherence length is substantially shortened.Comment: 5 pages, 3 figure

Gating a single-molecule transistor with individual atoms

Transistors, regardless of their size, rely on electrical gates to control the conductance between source and drain contacts. In atomic-scale transistors, this conductance is sensitive to single electrons hopping via individual orbitals1, 2. Single-electron transport in molecular transistors has been previously studied using top-down approaches to gating, such as lithography and break junctions1, 3, 4, 5, 6, 7, 8, 9, 10, 11. But atomically precise control of the gate—which is crucial to transistor action at the smallest size scales—is not possible with these approaches. Here, we used individual charged atoms, manipulated by a scanning tunnelling microscope12, to create the electrical gates for a single-molecule transistor. This degree of control allowed us to tune the molecule into the regime of sequential single-electron tunnelling, albeit with a conductance gap more than one order of magnitude larger than observed previously8, 11, 13, 14. This unexpected behaviour arises from the existence of two different orientational conformations of the molecule, depending on its charge state. Our results show that strong coupling between these charge and conformational degrees of freedom leads to new behaviour beyond the established picture of single-electron transport in atomic-scale transistors

Cancer risks from arsenic in drinking water.

Ingestion of arsenic, both from water supplies and medicinal preparations, is known to cause skin cancer. The evidence assessed here indicates that arsenic can also cause liver, lung, kidney, and bladder cancer and that the population cancer risks due to arsenic in U.S. water supplies may be comparable to those from environmental tobacco smoke and radon in homes. Large population studies in an area of Taiwan with high arsenic levels in well water (170-800 micrograms/L) were used to establish dose-response relationships between cancer risks and the concentration of inorganic arsenic naturally present in water supplies. It was estimated that at the current EPA standard of 50 micrograms/L, the lifetime risk of dying from cancer of the liver, lung, kidney, or bladder from drinking 1 L/day of water could be as high as 13 per 1000 persons. It has been estimated that more than 350,000 people in the United States may be supplied with water containing more than 50 micrograms/L arsenic, and more than 2.5 million people may be supplied with water with levels above 25 micrograms/L. For average arsenic levels and water consumption patterns in the United States, the risk estimate was around 1/1000. Although further research is needed to validate these findings, measures to reduce arsenic levels in water supplies should be considered

Toksikološka svojstva citrinina

Citrinin (CTN) is a nephrotoxic mycotoxin produced by several fungal strains belonging to the genera Penicillium, Aspergillus, and Monascus. It contaminates various commodities of plant origin, cereals in particular, and is usually found together with another nephrotoxic mycotoxin, ochratoxin A (OTA). These two mycotoxins are believed to be involved in the aetiology of endemic nephropathy. In addition to nephrotoxicity, CTN is also embryocidal and fetotoxic. The genotoxic properties of CTN have been demonstrated with the micronuleus test (MN), but not with single-cell gel electrophoresis. The mechanism of CTN toxicity is not fully understood, especially not whether CTN toxicity and genotoxicity are the consequence of oxidative stress or of increased permeability of mitochondrial membranes. CTN requires complex cellular biotransformation to exert mutagenicity. Compared with other mycotoxins, CTN contamination of food and feed is rather scarce. However, it is reasonable to believe that humans are much more frequently exposed to CTN than generally accepted, because it is produced by the same moulds as OTA, which is a common contaminant of human food all over the world. At present, there are no specifi c regulations either in Croatia or in the European Union concerning CTN in any kind of commodity.Citrinin (CTN) nefrotoksičan je mikotoksin koji proizvode različiti sojevi plijesni iz rodova Penicillium, Aspergillus i Monascus. CTN se može naći u različitim namirnicama biljnog podrijetla, osobito u žitaricama i obično se nalazi zajedno s drugim nefrotoksičnim mikotoksinom, okratoksinom A (OTA). Pretpostavlja se da je izloženost ovim mikotoksinima povezana s nastankom endemske nefropatije. Osim što je nefrotoksičan, CTN je još i embricidan i fetotoksičan. Na genotoksičnost citrinina upućuje pozitivan mikronukleusni test na različitim vrstama staničnih kultura, iako je kometski test negativan. Mutagenost CTN-a očituje se na različitim vrstama stanica samo ako se pridodaju stanični aktivatori kao npr. S9-mix. Mehanizam toksičnosti CTN-a nije potpuno razjašnjen pa još uvijek traje znanstvena rasprava je li njegova toksičnost i genotoksičnost posljedica oksidacijskog stresa ili povećane permeabilnosti mitohondrijskih membrana. U dostupnoj literaturi podaci o kontaminiranosti hrane i krmiva ovim mikotoksinom mnogo su rjeđi od onih za druge mikotoksine. Može se pretpostaviti da su ljudi često izloženi ovom mikotoksinu zato što ga proizvode iste plijesni koje proizvode i OTA, a one kontaminiraju hranu po cijelom svijetu. U Hrvatskoj i u zemljama Europske Unije ne postoje zakonske odredbe o dopuštenim granicama CTN-a u bilo kojoj vrsti hrane

The sources of phosphorus for the phosphatic rocks in the Toyoma Formation, Northeastern Japan

The apatite in the phosphatic rocks of the Toyoma Formation is carbonate fluorapatite highly enriched in Ce and Y. The Ce and Y enrichment of the apatite suggests that the source of phosphorus is biogenic phosphate mineral debris such as fish bones, teeth and scales rather than phosphorus-bearing organic matter. The spatially and stratigraphically limited distribution of the phosphatic rocks in the formation is in accord with this view.ArticleJournal of the Faculty of Science Shinshu University 39:19-24(2005)departmental bulletin pape