Bose-Einstein Condensation in Liquid 4He in Vycor

We present neutron scattering measurements of Bose-Einstein condensation (BEC) in liquid ⁴He confined in Vycor. The data show clear evidence of a condensate in Vycor with a condensate fraction comparable to that of bulk superfluid ⁴He, approximately 7.5% at low temperature and SVP. The temperature dependence of n₀(T) is also similar to that in the bulk with critical temperature for BEC, T_BEC, in the range 1.80BEC<2.05 K. The data are not accurate enough to show whether T_BEC for Vycor is the same or greater than the depressed critical temperature for superfluidity, T_c=1.95 K.     

Losses in diamond in the millimeter range

A theoretical and experimental investigation is made of the magnitude and nature of the dielectric losses in weakly absorbing synthetic diamonds in the wavelength range 1.75–6.8 mm at temperatures T=20–500 °C. Some samples exhibited extremely low losses (tan δ <10⁻⁵) which makes plasma-chemically deposited diamond wafers suitable for fabricating windows for megawatt continuous gyrotrons. It is shown that in principle, a further substantial reduction in losses can be achieved. Pis’ma Zh. Tekh. Fiz. 25, 85–89 (April 12, 1999)     

International Co-operation in Science and in Social Sciences as Reflected in Multinational Papers Indexed in SCI and SSCI

The paper presents a comparative analysis of publications, co-authored by Polish and foreign researchers, selected from seven annual files ofScience Citation Index and Social Sciences Citation Index (CD-ROM Editions 1992–1998). Information obtained from SCI and SSCI were elaborated, completed, coded and entered in two “international files” designed for analytical purposes. It was found that the number of internationally co-authored papers was many times higher (18982 records) in science than in social sciences (342 records). The share of these “international papers” in the “Polish files” increased in the time under review, but for those derived from SCI was also higher (39.1 – 46.0%) than in case of SSCI (22.4 – 37.0%). Results of the analysis include countries of foreign partners and affiliation of domestic co-authors, as well as, subject structure of both international files. Observed differences in the scale of international co-operation in science and in social sciences are being the matter under discussion. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cracking resistance in welded joints in tubular specimens

Summary An apparatus is described for automatic welding of ring joints in tubular specimens, which is based on an A-825M welding apparatus working in a protective gas.Twelve forms of welded joints in tubular specimens have been tested, which have been made from steels 40Kh and 30KhGSA after quenching and high annealing and from steels 35 and St3 after normalization. K_c in the joint is less by about a factor three than the resistance in the initial metal. The wide spread in the values (K_c = 19.3–47.4 MPa · m) is due to the poor weldability of the inhomogeneous materials, in which there are defects in the weld structure (unwelded spots, inclusions, pores, cracks, and so on). The viability in welded constructions must be forecast from the cracking resistance in the joints, not in the initial material.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 26, No. 4, pp. 108–109, July–August, 1990.     

Education in sustainable production in US universities

The evolution and current status of sustainable production education (SPE) in the United States is reviewed, both as a discrete entity and as an intersection of multiple disciplines. This paper (a) examines the current array of compatible and conflicting theories that guide the alternative approaches to SPE, (b) reviews the wide array of applications to which such theories and associated methodologies have been applied, and (c) presents a case study of the emerging interdisciplinary approach to SPE at Purdue University in West Lafayette, Indiana, USA, and its network of national and international collaborators. North Atlantic Treaty Organization (NATO) Committee on the Challenges to Modern Society (CCMS). Pilot study on clean products and processes Annual meeting, May 2–6, 2004, Budapest, Hungary

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Crack growth in structural adhesive joints in aqueous environments

The adhesive fracture energy, G _c , of metallic joints, bonded with a rubber-toughened epoxy adhesive, has been measured using monotonically-loaded tests. Such tests have been conducted in various relative humidities and in water, at 21 °C. Two surface pretreatments have been employed for the substrates prior to bonding: a simple grit-blast and degrease (‘GBD’) pretreatment or a grit-blast, degrease and silane primer (‘GBS’) pretreatment. The joints were formed using metallic substrates which were either (a) aluminium-alloy substrates, (b) steel substrates, or (c) ‘dissimilar’ substrates (i.e. one substrate being aluminium-alloy with the other one being steel). For both test environments, when G _c was plotted against the crack velocity, three regions of fracture behaviour could be distinguished. At low rates of displacement the crack grew in a stable manner, visually along the interface, and relatively low crack velocities could be readily measured. This was termed ‘Region I’ and here the value of G _c measured in the aqueous environment was relatively low compared to that measured in a relatively dry environment of 55% relative humidity. On the other hand, at relatively high rates of displacement the crack always grew in a stick-slip manner mainly cohesively in the adhesive layer at approximately 20 km/min. This was termed ‘Region III’, and here the value of G _c was relatively high and independent of the environmental test conditions employed. In this region the crack was considered to grow faster than the water molecules were able to reach the crack tip, which explains the independence of G _c upon the test environment. In between ‘Region I’ and ‘Region III’, a transition region was observed which was designated as ‘Region II’. The major effect of the ‘GBS’ pretreatment, compared to the ‘GBD’ pretreatment, was to increase the value of G _c both in ‘Regions I and III’, although the presence of the silane primer had the far greater effect in ‘Region I’.     

Solubility of lanthanum in strontium titanate in oxygen-rich atmospheres

Perovskite (ABO₃)-type lanthanum substituted strontium titanate ceramics (lanthanum content x), which had been sintered in pure oxygen at 1400 °C, were investigated from x = 0 up to x = 0.6 by light optical and scanning electron microscopic means in conjunction with X-ray analysis, X-ray diffraction, and pyconometry in order to determine the mechanism being responsible for the compensation of the electronic excess charge resulting from the "donor" lanthanum. A pure strontium vacancy compensation mechanism was observed for lanthanum contents up to x = 0.3. Above x = 0.4 titanium vacancies occur additionally but their concentration remains negligible compared to the predominating strontium vacancies. No indication of a solubility limit of lanthanum at x = 0.4, as stated in former works was observed. At x = 0.5 and 0.6 the lattice structure was found to be slightly distorted, tetragonally and orthorhombically, respectively. The lattice parameter obeys Vegard’s law up to the end member La_2/3□_1/3TiO₃ (□: vacant site). These results were completely confirmed by pycnometry data. This revised version was published online in November 2006 with corrections to the Cover Date.     

Losses in superconducting cables in pulsed magnetic fields

Measurements have been carried out of superconducting cables of different types in pulsed magnetic fields. Three types of samples have been made from multifilamentary Nb_0.5  Ti_0.5 superconductors: one, a cluster of isolated wires; two, a double-layer twisted flat cable; and three, one-layer twisted tube samples. Dependences have been studied of ac losses on the amplitude, direction and change velocity of the magnetic field as well as on the diameter of filaments and twist pitch. It is shown that the ac losses in unsoldered samples are close to those in the cluster of isolated wires.     

Improved angiogenic cell penetration in vitro and in vivo in collagen scaffolds with internal channels

Porous scaffolds are limited in volume due to diffusion constraint and delay of vascular network formation. Channels have the potential to speed up cellular penetration. Their effectiveness in improving angiogenic cell penetration was assessed in vitro and in vivo in 3-D collagen scaffolds. In vitro, channelled and non-channelled scaffolds were seeded with vascular smooth muscle cells. Results demonstrated that the scaffolds supported angiogenic cell ingrowth in culture and the channels improved the depth of cell penetration into the scaffold (P < 0.05). The cells reside mainly around and migrate along the channels. In vivo, channels increased cell migration into the scaffolds (P < 0.05) particularly angiogenic cells (P < 0.05) resulting in a clear branched vascular network of microvessels after 2 weeks in the channelled samples which was not apparent in the non-channelled samples. Channels could aid production of tissue engineered constructs by offering the possibility of rapid blood vessel infiltration into collagen scaffolds.     

Kinematical transformations in amorphous selenium alloys used in xerography

Differential scanning calorimetric (DSC) studies were carried out on xerographic photoreceptor materials of amorphous selenium (a-Se), a-Se_1&#x2203-xTe_x and a-Se:0.5 wt% As alloys with various amounts of chlorine doping. Glass transformation kinetics of bulk and vapour-deposited film samples were essentially identical indicating a similar amorphous structure for both forms. The glass transition temperature,T _g, in the a-Se_1&#x2203-xTe_xsystem was found to increase monotonically with the tellurium content up to 13 wt% which was accompanied by a fall in the activation energy,E _gl, for the structural relaxation. 0.5wt% As increasedT _g, whereas chlorine doping in the amounts used (100 ppm) had no effect onT _g. Crystallization exotherms were analysed using the Kissinger method which was shown to remain a valid analysis by integrating the fundamental Kolmogoroff equation describing crystallization transformations by nucleation and growth. The signifiance of the activation energy,E _A, and the frequency factor,C ₀, in the Kissinger analysis is discussed and used in interpreting the different crystallization behaviour exhibited by the various alloys. The apparent activation energy,E _A, of the crystallization kinetics was found to fall with the temperature range accessed in the DSC experiment. When other authors' previous crystallization studies by other methods were also considered, then 1/E _A was found to fall nearly linearly with the mean reciprocal temperature, 1/T, used in the experiment. It is argued that this behaviour arises if the crystal growth rate scales with the inverse viscosity of the melt and the latter is described by a Vogel-Tammann-Fulcher type of behaviour. The additives tellurium and arsenic retard the crystallization essentially by increasing the viscosity. Chlorine doping was also found to have an inhibitory effect but due probably to a change in the nucleation kinetics, rather than a viscosity rise.     

Plasma density in discharge sustained in inhomogeneous gas flow by high-power radiation in the terahertz frequency range

We have measured the density of plasma (electron concentration) in discharge maintained in inhomogeneous argon flow under the action of high-power pulsed radiation of gyrotron (frequency, 0.67 THz; power 40 kW; pulse duration, 20–30 μs) in a range of background gas pressures in the discharge chamber from 10^–3 to 300 Torr. The electron concentration at low pressures (10^–3 to 7 Torr) was determined using Starkeffect induced broadening of the H_α atomic emission line (656.3 nm) of hydrogen present in discharge as a small impurity in residual gases. The maximum observed Stark broadening of the H_α line corresponded to a plasma density on the order of 2 × 1016 cm^–3, which exceeded the critical value for the given frequency of radiation sustaining the discharge. At background pressures above 7 Torr, the plasma density was estimated from analysis of the spatiotemporal patterns and waveforms of discharge glow in the visible spectral range. These estimations gave electron concentrations on the level of (1–2) × 10¹⁵ cm^–3.     

Structural changes in S&T research in India

Before India became an independent country, its scientists and policy makers could foreseethe importance of science in its development, and accordingly a number of research anddevelopment (R&D) institutions were established. However during these five decades ofindependence, the choice between basic sciences and technology was always a subject of debate.It will be appropriate now to examine the changing patterns of Science and Technology (S&T)manpower growth to find out the ground truth reality. The present study pertains to the analysis ofS&T outturn data in various fields of scientific research that can provide a base for S&T planningand policy making. These S&T indicators will be helpful in estimating future requirements, whichin turn can be useful to a great extent in science and technology policy formulation. Theseestimates and future projections are based on mathematical modelling of the data pertaining to theoutturn of highly qualified Scientific and Technical (S&T) personnel in India from differentfaculties over the period 1990-1998. From the trend analysis it is evident that research is no moreperceived as an interesting career except in the field of engineering and medicine. The findingsfurther suggest that there is a noticeable shift from basic sciences to technology.     

Feshbach Shape Resonance in Multiband Superconductivity in Heterostructures

We report experimental data showing the Feshbach shape resonance in the electron doped MgB₂ where the chemical potential is tuned by Al, Sc, and C substitutions. The scaling of the critical temperature T _c as a function of the Lifshitz parameter z = E _Γ−E _F, where E _F is the chemical potential and E _Γ is the energy of the Γ critical point where the σ Fermi surface changes from the 3D to a 2D topology, is reported. The resonant amplification of T _c(z) driven by the interband pairing is assigned to a Feshbach shape resonance characterized by quantum superposition of pairs in states corresponding to different spatial location and different parity. It is centered at z = 0 where the chemical potential is tuned to a Van Hove-Lifshits feature for the change of Fermi surface dimensionality in the electronic energy spectrum in one of the subbands. In this heterostructure at atomic limit the multiband superconductivity is in the clean limit because the disparity and negligible overlap between electron wavefunctions in different subbands suppresses the single electron interband impurity scattering rate. The emerging scenario from these experimental data suggests that the Feshbach shape resonance could be the mechanism for high T _c in particular nanostructured architectures.     

The parameters of nonequilibrium microwave discharge in nitrogen in a tube in a rectangular waveguide

Computer codes are developed for the processing of emission spectra of nonequilibrium plasma in nitrogen for the purpose of obtaining information about the translational T _g and rotational T _rot temperatures, the populations of vibrational levels in the ground electron and electron-excited states, the electron energy distribution function, the electron concentration N _e , and the electric field intensity E. The computer codes are used to determine the parameters of microwave-discharge plasma in nitrogen in discharge systems of two types, namely, in a discharge tube (with a radius of 1 cm), which crosses a rectangular waveguide (plasmatron on the H ₁₀ wavelength, at a pressure of 1.7 torr and absorbed power density of 1.5 W/cm³), and in a discharge section of similar structure on the basis of prismatic resonator (at a pressure of 1.0 torr and absorbed power density of 0.4 W/cm³). The mechanisms of population of the N₂(C ³Π_u) state are treated.     

Trends in Russian research output in post-Soviet era

Recently, the Russian government has ordered evaluation and reform of the basic research system. As a consequence, the number of research staff at the Russian Academy of Sciences will be reduced by 20% by 2007. The basis for research evaluation and institute budgeting will be bibliometric indicators. In view of these changes we look at the Russian publication output and argue that

High-temperature cracking resistance in cast steel in reforming oven tubes

Summary Results are given from high-temperature tests (770, 870, 920, and 960°C) to estimate the short-time and cyclic cracking resistance for cast NK-40 steel tubes from reforming ovens in the initial state and after use for 75,400 h. The crack growth resistance in static loading has been determined from the crack resistance limit, and in cyclic loading from the kinetic diagrams for the fatigue failure in terms of the crack growth ratev against the scale of the nominal stress intensity coefficient K. Metallography shows that there are differences in structure in the various states, and material that has been used has pores and microcracks, whose numbers are largest in the inner wall layers. Cyclic tests with constant K show substantial increase in the crack growth rate in the defective material.The cracking stability limit falls as the test temperature rises, while the fatigue crack growth rate increases, particularly above 920°C. Increased asymmetry in the loading cycle (R=–1; –0.5; 0; 0.4) is accompanied by deterioration in the cyclic cracking resistance. There are two opposite trends in the effects of loading frequency (f=0.001–10 Hz) on the failure kinetics: in the high-amplitude loading range, reduction inf increases the crack growth rate, while in the low-amplitude range, there is a decrease. The results are explained in terms of creep and fatigue crack opening.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 26, No. 2, pp. 68–74, March–April, 1990.     

Capsaicin pretreatment enhanced the bioavailability of fexofenadine in rats by P-glycoprotein modulation: in vitro,in situ and in vivo evaluation

Background and objective: Capsaicin is the main pungent principle present in chili peppers has been found to possess P-glycoprotein (P-gp) inhibition activity in vitro, which may have the potential to modulate bioavailability of P-gp substrates. Therefore, purpose of this study was to evaluate the effect of capsaicin on intestinal absorption and bioavailability of fexofenadine, a P-gp substrate in rats.

Methods: The mechanistic evaluation was determined by non-everted sac and intestinal perfusion studies to explore the intestinal absorption of fexofenadine. These results were confirmed by an in vivo pharmacokinetic study of oral administered fexofenadine in rats.

Results: The intestinal transport and apparent permeability (P_app) of fexofenadine were increased significantly by 2.8 and 2.6 fold, respectively, in ileum of capsaicin treated rats when compared to control group. Similarly, absorption rate constant (K_a), fraction absorbed (F_ab) and effective permeability (P_eff) of fexofenadine were increased significantly by 2.8, 2.9 and 3.4 fold, respectively, in ileum of rats pretreated with capsaicin when compared to control group. In addition, maximum plasma concentration (C_max) and area under the concentration-time curve (AUC) were increased significantly by 2.3 and 2.4 fold, respectively, in rats pretreated with capsaicin as compared to control group. Furthermore, obtained results in rats pretreated with capsaicin were comparable to verapamil (positive control) treated rats.

Conclusions: Capsaicin pretreatment significantly enhanced the intestinal absorption and bioavailability of fexofenadine in rats likely by inhibition of P-gp mediated cellular efflux, suggesting that the combined use of capsaicin with P-gp substrates may require close monitoring for potential drug interactions.     

Vortices in superconductors

In type II superconductors where the London penetration depthλ is larger than the coherence lengthξ, there is a possibility of flux penetration inside the sample for magnetic field greater than \(H_{0_1 } \left( { = \frac{{\phi _0 }}{{4\pi \lambda ^2 }}ln \lambda /\xi , \phi _0 = \frac{{hc}}{{2e}}} \right).\) The flux penetrates in the form of vortices with core of sizeξ. However these vortices differ from those in superfluid He⁴ in variation of currentj(r) circulating around them. For superconductorsj(r) ～ 1/r only up to a distanceλ and then it falls exponentially whilev(r) ～ 1/r for all distances in superfluids. The reason is that in superconductors vortex carries a magnetic flux which is screened by conduction electrons. This coupling of order parameter field (the pairing wavefunction) with the gauge field has many interesting implications for superconductors and for non-Abelian gauge theories. Some examples are as follows:

1. The energy of the vortices is reduced. The energy of vortex of lengthL (ind = 3 sample) is of orderL lnL for a superfluid, is of orderL in a superconductor, and (in ad = 2 sample) the energy of a vortex point which diverges like lnR (whereR is the size of the sample) in a superfluid becomes finite in a superconductor.
2. The superconducting-normal transition in three dimension is very weak first order, because the fluctuations of the gauge field, when summed over, add to Ginzburg Landau free energy a term proportional to |ψ|³, whereψ is the order parameter.
3. Because of the lnr behaviour of interaction energy of vortices, a two-dimensional superfluid sample can exhibit a Kosterlitz-Thouless type transition whereas a strictlyd = 2 superconductors should not have any. However for dirty superconducting films whereλ is large vortex binding-unbinding transition can be observed with quite a rich phase diagram.

The paper presented at the discussion meeting discusses the above in detail. Here we give only a brief summary of results and some relevant references.