Thek-partitioning problem

Thek-partitioning problem is defined as follows: Given a set of items {I ₁,I ₂,...,I _n} where itemIj is of weightwj 0, find a partitionS ₁,S ₂,...,S _m of this set with ¦S _i ¦ =k such that the maximum weight of all subsetsS _i is minimal,k-partitioning is strongly related to the classical multiprocessor scheduling problem of minimizing the makespan on identical machines. This paper provides suitable tools for the construction of algorithms which solve exactly the problem. Several approximation algorithms are presented for this NP-hard problem. The worst-case behavior of the algorithms is analyzed. The best of these algorithms achieves a performance bound of 4/3.     

Synthesis,conductivity, and the crystal structure of a new stable metal, β″-(<Emphasis Type="Italic">DOEO</Emphasis>)<Subscript>2</Subscript>HSeO<Subscript>4</Subscript> · H<Subscript>2</Subscript>O

The stable metal β″-(DOEO)₂HSeO₄ · H₂O I) based on a new donor compound, 3,4-(1,4-dioxanediyl-2,3-dithio)-3′,4′-ethylenedioxo-2,5,2′,5′-tetrathiafulvalene] (DOEO), is synthesized and structurally characterized for the first time. The synthesis is performed by the electrocrystallization technique (direct current density j = 2 × 10^?6 A/cm²). The crystals are triclinic, and the unit cell parameters are as follows: a = 5.495(1) Å, b = 9.715(2) Å, c = 16.878(3) Å, α = 83.52(3)°, β = 82.54(3)°, γ = 73.51(3)°, Z = 1, and space group \(P\bar 1\). The salt has a layered structure. The DOEO^1/2+ radical cation layers are aligned parallel to the ab planes. The HS_eO ₄ ^? · H₂O solvated anions are located in channels along the a axis and are disordered over two positions near the center of symmetry (1/2 0 0) with a probability of 50%. The conductivity of the salt is equal to 300–400 Ω^?1 cm^?1 at room temperature and increases upon cooling to the boiling point of liquid helium (4.2 K) by a factor of 100–200 depending on the sample.     

Crystal structure of the new radical cation salt (<Emphasis Type="Italic">DOET</Emphasis>)<Subscript>4</Subscript>[Fe(CN)<Subscript>5</Subscript>NO]<Subscript>1.25</Subscript>(C<Subscript>6</Subscript>H<Subscript>5</Subscript>Cl)<Subscript>0.75</Subscript>

A new radical cation salt based on 4,5-(1,4-dioxanediyl-2,3-dithio)-4′,5′-ethylenedithiotetrathiafulvalene (DOET) with the photochromic anion [Fe(CN)₅NO]^2?, namely, (DOET)₄[Fe(CN)₅ NO]_1.25(C₆H₅Cl)_0.75, is synthesized. Single crystals of this salt are studied using X-ray diffraction [a = 10.398(2) Å, b = 11.168(2) Å, c = 18.499(4) Å, α = 103.14(3)°, β = 92.80(3)°, γ = 106.02(3)°, V = 1996.3(7) ų, space group \(P\bar 1\), and Z = 1]. In the structure, radical cation layers alternate with anion layers along the c axis. The centrosymmetric dimers are formed by DOET radical cations in the donor layer with packing of the β type. Like the vast majority of DOET-based salts, the new salt possesses semiconductor properties.     

Crystal structure of double vanadates Ca9 R(VO4)7. II. R = Tb, Dy, Ho, and Y

Crystal structures of the compounds Ca₉ R(VO₄)₇ (R = Tb (I), Dy (II), Ho (III), and Y (IV) have been studied by the method of the full-profile analysis. All the compounds are crystallized in the trigonal system (sp. gr. R 3 c, Z = 6) with the unit-cell parameters (I) a = 10.8592(1), c = 38.035(1), V = 3884.2(2) ų; (II) a = 10.8564(1), c = 38.009(1) Å, V = 3879.6(2) ų, (III) a = 10.8565(1) and c = 37.995(1) Å, V = 3878.3(2) ų, and (IV) a = 10.8588(1), c = 37.995(1) Å, V = 3879.9(2) ų. In structures I–IV, rare earth and calcium cations occupy three positions—M(1), M(2), and M(5). Rare earth cations occupy the R ³⁺ positions almost in the same way: 2.7–2.6(2) cations in the M(1) position; 2.7–2.3(2) cations in the M(2) position, and 0.6–1.0(1) cation in the M(5) position. At the same time, the occupancy of the M(5) position regularly increases with a decrease of the R ³⁺ radius.     

Gold nanoparticles enhance the anti-leukemia action of a 6-mercaptopurine chemotherapeutic agent

6-mercaptopurine and its riboside derivatives are some of the most widely utilized anti-leukemic and anti-inflammatory drugs. Their short biological half-life and severe side effects limit their use. A new delivery method for these drugs based on 4-5 nm gold nanoparticles can potentially resolve these issues. We have found substantial enhancement of the antiproliferative effect against K-562 leukemia cells of Au nanoparticles bearing 6-mercaptopurine-9-beta-d-ribofuranoside compared to the same drug in typically administered free form. The improvement was attributed to enhanced intracellular transport followed by the subsequent release in lysosomes. Enhanced activity and nanoparticle carriers will make possible the reduction of the overall concentration of the drug, renal clearance, and, thus, side effects. The nanoparticles with mercaptopurine also showed excellent stability over 1 year without loss of inhibitory activity.     

Reversible loading and unloading of nanoparticles in "exponentially" growing polyelectrolyte LBL films

The exponentially growing layer-by-layer (LBL) films made from poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used to load and unload the CdTe nanoparticles (NPs). The reversible loading of NPs were investigated through UV-vis studies and further confirmed by confocal microscopy. In addition the LBL films were also compared for the release kinetics for pH 9 and 7 and films capped with (PDDA-PSS)10 layers. The amount of released particles at pH 9 was found to be at least 2 orders of magnitude higher than those at pH 7 and with (PDDA-PSS)10 capped layers after 25 h. This variation in film response for CdTe-particle release presents a route for studies in which highly swollen exponentially growing LBL films can be loaded with functionalized NPs for biological applications and explored as carriers to hold the NPs inside the films for self-assembly.     

Super-Strong Hydrogel Composites Reinforced with PBO Nanofibers for Cartilage Replacement

Cartilage replacement materials exhibiting a set of demanding properties such as high water content, high mechanical stiffness, low friction, and excellent biocompatibility are quite difficult to achieve. Here, poly(p-phenylene-2,6-benzobisoxazole) (PBO) nanofibers are combined with polyvinyl alcohol (PVA) to form a super-strong structure with a performance that surpasses the vast majority of previously existing hydrogels. PVA–PBO composites with water contents in the 59–76% range exhibit tensile and compressive moduli reaching 20.3 and 4.5 MPa, respectively, and a coefficient of friction below 0.08. Further, they are biocompatible and support the viability of chondrocytes for 1 week, with significant improvements in cell adhesion, proliferation, and differentiation compared to PVA. The new composites can be safely sterilized by steam heat or gamma radiation without compromising their integrity and overall performance. In addition, they show potential to be used as local delivery platforms for anti-inflammatory drugs. These attractive features make PVA–PBO composites highly competitive engineered materials with remarkable potential for use in the design of load-bearing tissues. Complementary work has also revealed that these composites will be interesting alternatives in other industrial fields where high thermal and mechanical resistance are essential requirements, or which can take advantage of the pH responsiveness functionality.     

Calculation of the relaxation time from the frequency spectra of ferrites

A method for determining the relaxation times of the magnetic moments of ferrites from inverse Fourier transforms is suggested. The effect of the alternating external magnetic field strength on the relaxation times was studied. It was found that the dispersion and absorption ranges in the magnetic spectra are associated with changes in the relaxation times of magnetic moments of ferromagnets.     

Overview of the application of nanosecond electron beams forradiochemical sterilization

Problems concerning the use of nanosecond electron beams for sterilization of hermetically packed objects, and powdered or granulated materials, are discussed. The advantages and disadvantages of this type of radiation sterilization are demonstrated. The results are of interest to researchers who study the mechanism by which nanosecond electron beams act on microorganisms. It is worth considering repetitively pulsed electron accelerators as highly promising systems for use in commercial sterilization applications. Technologies and setups for the radiochemical sterilization (RCS) of medical glassware for blood products, beer bottles, bone meal used in food industry, medical instruments (surgical needles, systems for human kidneys), and of the external packaging for some biological materials used in ophthalmology are discussed. Such applications have been developed based on the use of the URT-0.2 and URT-0.5 repetitively nanosecond-pulsed electron accelerators. The observed sterilization of areas shaded from line-of-site irradiation and of the bottoms of, for example, glassware cannot be attributed to radiation sterilization alone, since the glass thickness was much larger than the range of electrons. Therefore, it can be conjectured that the demonstrated sterilization effect is due both to the electron beam and to the ozone and chemical radicals produced by the beam. Thus, one may introduce the notion of RCS