A survey of nitrate and nitrite content of fruit and vegetables grown in Slovenia during 1996-2002

Monitoring of nitrate (NO₃^-) and nitrite (NO₂^-) content in agricultural products in Slovenia has been carried out since 1996. The results of monitoring over the period 1996-2002 are presented. During this time 924 samples of 14 different agricultural products (potato, lettuce, apples, carrot, silage maize, cabbage, grapes, peaches, string beans, cereals, pears, cucumbers, strawberries and tomato) were analysed. The samples were taken at the time of maturity directly from growing sites and they were analysed using segmented flow analysis. The average nitrate contents were the highest in lettuce (1074 mg kg^-1), cabbage (881 mg kg^-1), string beans (298 mg kg^-1) and carrot (264 mg kg^-1), and they were moderately high in potato (158 mg kg^-1), silage maize (122 mg kg^-1), strawberries (94 mg kg^-1), cucumbers (93 mg kg^-1) and cereals (49 mg kg^-1). Low nitrate contents (below 6 mg kg^-1) were found in fruit (grapes, peaches, apples and pears) and tomato. With the exception of cereals (8.9 mg kg^-1), apples (1.5 mg kg^-1), potato (1.2 mg kg^-1) and pears (1.0 mg kg^-1) the content of nitrites did not exceed 0.5 mg kg^-1. It may be concluded that the results of the monitoring were in most cases similar to the results of investigations obtained in other countries.     

Influence of Particle Size Distribution,Moisture Content,and Particle Shape on the Flow Properties of Bulk Solids

Abstract

There has been a great deal of research on characterising bulk solids. However, some of the characteristics, particularly the time‐dependent and random changes of properties, still remain insufficiently understood. The focus of this article is to study the influence of particle size, size distribution, moisture content, and particle shape on the unconfined yield strength of bulk solids. We present some interesting results about the influence of the particle size distribution on the unconfined yield strength of a bulk solid and a new method for determining the influence of particle shape on the unconfined yield strength of a bulk solid, which was made possible by the design and use of a novel attritor.     

Strong Hydrogen Bonds in Acetylenedicarboxylic Acid Dihydrate

Acetylenedicarboxylic acid dihydrate (ADAD) represents a complex with strong hydrogen bonding between the carboxylic OH and the water molecule. An X-ray re-examination of the ADAD crystal structure confirms the O^…O distance of the short hydrogen bonds, and clearly shows different bond lengths between the two oxygen atoms with respect to the carbon atom in the carboxyl group, indicating a neutral structure for the complex. The neutral structure was also confirmed by vibrational spectroscopy, as no proton transfer was observed. The diffraction studies also revealed two polymorph modifications: room temperature (α) and low temperature (β), with a phase transition at approximately 4.9 °C. The calculated vibrational spectra are in satisfactory agreement with the experimental spectra. A comparison of the structure and the vibrational spectra between the ADAD and the oxalic acid dihydrate reveals some interesting details. The crystal structures of both crystal hydrates are almost identical; only the O^…O distances of the strongest hydrogen bonds differ by 0.08 Å. Although it was expected that a larger O^…O spacing in the ADAD crystal may significantly change the infrared and Raman spectra, especially for the frequency and the shape of the acidic OH stretching vibration, both the shape and frequency are almost identical, with all subpeaks topped on the broad OH stretching vibration. The O^…O distance dependent are only in- and out-of-plane OH deformations modes. The presence of polarons due to the ionized defects was not observed in the vibrational spectra of ADAD. Therefore, the origin of the broad OH band shape was explained in a similar way to the acid dimers. The anharmonicity of a potential enhances the coupling of the OH stretching with the low-frequency hydrogen bond stretching, which, in addition to the Fermi resonance, structures the band shape of the OH stretching. The fine structure found as a superposition of a broad OH stretching is attributed to Davydov coupling.     

Biocompatibility and Mechanical Stability of Nanopatterned Titanium Films on Stainless Steel Vascular Stents

Nanoporous ceramic coatings such as titania are promoted to produce drug-free cardiovascular stents with a low risk of in-stent restenosis (ISR) because of their selectivity towards vascular cell proliferation. The brittle coatings applied on stents are prone to cracking because they are subjected to plastic deformation during implantation. This study aims to overcome this problem by using a unique process without refraining from biocompatibility. Accordingly, a titanium film with 1 µm thickness was deposited on 316 LVM stainless-steel sheets using magnetron sputtering. Then, the samples were anodized to produce nanoporous oxide. The nanoporous oxide was removed by ultrasonication, leaving an approximately 500 nm metallic titanium layer with a nanopatterned surface. XPS studies revealed the presence of a 5 nm-thick TiO₂ surface layer with a trace amount of fluorinated titanium on nanopatterned surfaces. Oxygen plasma treatment of the nanopatterned surface produced an additional 5 nm-thick fluoride-free oxide layer. The samples did not exhibit any cracking or spallation during plastic deformation. Cell viability studies showed that nanopatterned surfaces stimulate endothelial cell proliferation while reducing the proliferation of smooth muscle cells. Plasma treatment further accelerated the proliferation of endothelial cells. Activation of blood platelets did not occur on oxygen plasma-treated, fluoride-free nanopatterned surfaces. The presented surface treatment method can also be applied to other stent materials such as CoCr, nitinol, and orthopedic implants.     

Friction on a single MoS2 nanotube

Friction was measured on a single molybdenum disulfide (MoS₂) nanotube and on a single MoS₂ nano-onion for the first time. We used atomic force microscopy (AFM) operating in ultra-high vacuum at room temperature. The average coefficient of friction between the AFM tip and MoS₂ nanotubes was found considerably below the corresponding values obtained from an air-cleaved MoS₂ single crystal or graphite. We revealed a nontrivial dependency of friction on interaction strength between the nanotube and the underlying substrate. Friction on detached or weakly supported nanotubes by the substrate was several times smaller (0.023 ± 0.005) than that on well-supported nanotubes (0.08 ± 0.02). We propose an explanation of a quarter of a century old phenomena of higher friction found for intracrystalline (0.06) than for intercrystalline slip (0.025) in MoS₂. Friction test on a single MoS₂ nano-onion revealed a combined gliding-rolling process.PACS, 62.20, 61.46.Fg, 68.37 Ps     

Layout design of manufacturable quantum-dot cellular automata

Quantum-dot cellular automaton (QCA) is an emergent technology that is not hindered by quantum effects that limit the scaling of CMOS technology, but instead employs them to perform computation. However, this brings its own impediments, such as the influence of the thermodynamic effects. Beside that, QCA has to be coupled with CMOS circuitry of different size features to enable clocking. We discussed all these facts and devised a floorplan which would facilitate manufacturability. Based on it we developed the process of QCA layout design and defined the design rules that must be considered in order to ensure correct operation. These instructions enable the automatization of designing a QCA circuit layout.     

G-quadruplex formation of oligonucleotides containing ALS and FTD related GGGGCC repeat

A largely increased number of GGGGCC repeats located in the non-coding region of C9orf72 gene have been identified as the leading cause of two related neurological disorders, familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). We examined G-quadruplex forming ability of GGGGCCrepeat containing oligonucleotides with four guanine tracts chosen as the smallest possible model to form a unimolecular G-quadruplex. These oligonucleotides are readily to folded into G-quadruplexes in the presence of K⁺ ions. However, the formation of multiple structures makes structural analysis challenging and time consuming. We observed that flanking sequences on 5'- and 3'-ends as well as mutations of loop residues have a profound effect on folding. Sequence d[(G₄C₂)₃G₄] was chosen for further scrutiny and optimization of nuclear magnetic resonance (NMR) spectroscopic properties with dG to 8Br-dG substitutions at specific positions in the sequence under different folding conditions. Expectedly, folding into desired predominant topology is facilitated when substituted residue adopted a syn conformation in the naturally-occurring structure. Single dG to 8Br-dG substitution at position 21 and fine tuning of folding conditions facilitate folding of d[(G₄C₂)₃GG^BrGG] into (mostly) a single G-quadruplex, and thus enable determination of its high-resolution structure by high-field NMR.

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高山庇护所 斯诺文尼亚

<正>建设单位:PD Ljubljana Matica项目计划:庇护所结构工程:AKT II, Hanif Kara, Edward Wilkes实施及现场协调:PD Ljubljana Matica,Matevz Jerman, Davor Rozman项目情况:2016年竣工主承包商:Permiz d.o.o., Bostjan Perme OFIS和AKT II的建筑师同哈佛大学设计研究生院、Freeaproved、PD Ljubljana Matica、Rieder和Rockwool的学生合作完成了这个项目。     

Electrochemical routes for environmentally friendly recycling of rare-earth-based (Sm–Co) permanent magnets

Journal of Applied Electrochemistry - The consumption of critical raw materials, especially those in permanent magnets of Nd–Fe–B and Sm–Co-type, has significantly grown in the...