Debonding of adhesive joints by means of microwave and induction heating processes

In this work, an innovative technique for adhesive joint separation that combines the use of a hybrid-modified adhesive with microwave (MW) or induction heating (IH) [1-3] processes is presented. Graphene nanoplatelets (GnPs) and iron oxide particles were used to modify a thermoplastic adhesive, polyolefin hot-melt adhesive by mean of a twin-screw extruder. This thermoplastic adhesive, already used for bonding automotive applications, was modified with both iron oxide and GnPs in order to enhance the electrical properties and the sensitivity to MW and IH. The mechanical and electrical properties together with the sensitivity of the modified adhesives to microwave or induction heating processes are investigated. Single Lap Joint (SLJ) specimens were used to evaluate the mechanical properties of the pristine and the modified adhesive. The mechanical tests illustrate that the maximum loads of modified adhesives decrease slightly. Tests conducted with microwave and induction heating processes showed that these two systems are able to melt the modified adhesive. Thus, the separation of bonded joints is possible with both systems. The temperature increase of the induction heating system is found to be more rapid than the microwaves but the latter system is energetically more efficient. Scanning Electron Microscope (SEM) was used to measure the particle distribution and to evaluate the differences between the manual mixed mode and the tween extruder system as preliminary analysis

Wide-band X-ray variability of GRS 1915+105 observed with BeppoSAX

The Galactic Microquasar GRS 1915+105 was observed by the Narrow Field Instruments onboard BeppoSAX in two pointings during year 2000. We present the preliminary results of wide-band study of the observed variability, carried out also with the wavelet analysis.Comment: 5 pages, 3 figures, AIP Conference Proceedings, Gamma-2001 Meeting, Baltimore, M D, April 200

Graviton Spectra in String Cosmology

We propose to uncover the signature of a stringy era in the primordial Universe by searching for a prominent peak in the relic graviton spectrum. This feature, which in our specific model terminates an $\omega^3$ increase and initiates an $\omega^{-7}$ decrease, is induced during the so far overlooked bounce of the scale factor between the collapsing deflationary era (or pre-Big Bang) and the expanding inflationary era (or post-Big Bang). We evaluate both analytically and numerically the frequency and the intensity of the peak and we show that they may likely fall in the realm of the new generation of interferometric detectors. The existence of a peak is at variance with ordinarily monotonic (either increasing or decreasing) graviton spectra of canonical cosmologies; its detection would therefore offer strong support to string cosmology.Comment: 14 pages, RevTex source and 6 figures.p

Inflation in Multidimensional Quantum Cosmology

We extend to multidimensional cosmology Vilenkin's prescription of tunnelling from nothing for the quantum origin of the observable Universe. Our model consists of a $D+4$-dimensional spacetime of topology ${\cal R}\times {\cal S}^3 \times{\cal S}^D$, with a scalar field (``chaotic inflaton'') for the matter component. Einstein gravity and Casimir compactification are assumed. The resulting minisuperspace is 3--dimensional. Patchwise we find an approximate analytic solution of the Wheeler--DeWitt equation through which we discuss the tunnelling picture and the probability of nucleation of the classical Universe with compactifying extra dimensions. Our conclusion is that the most likely initial conditions, although they do not lead to the compactification of the internal space, still yield (power-law) inflation for the outer space. The scenario is physically acceptable because the inner space growth is limited to $\sim 10^{11}$ in 100 e-foldings of inflation, starting from the Planck scale.Comment: RevTeX, 30 pages, 4 figures available via fax on request to [email protected], submitted to Phys. Rev.

A Cosmology of the Brane World

We develop a possible cosmology for a Universe with n additional spatial dimensions of variable scale, and an associated scalar field, the radion, which is distinct from the field responsible for inflation, the inflaton. Based on a particular ansatz for the effective potential for the inflaton and radion (which may emerge in string theory), we show that the early expansion of the Universe may proceed in three stages. First, the radion becomes trapped at a value much smaller than the size of the extra dimensions today. Second, the Universe expands exponentially, but with a Planck mass smaller than its present value. Because the Planck mass during inflation is small, density fluctuations in agreement with observations can arise naturally. Third, when inflation ends, the Universe reheats, and the radion becomes free to expand once more. During the third phase the Universe is ``radiation-dominated'' and tends toward a fixed-point evolutionary model in which the radion grows but the temperature remains unchanged. Ultimately, the radion becomes trapped once again at its present value, and a short period of exponential expansion, which we identify with the electroweak phase transition, ensues. Once this epoch is over, the Universe reheats to a temperature of order the electroweak scale, and the mature Universe evolves as in standard cosmological models. We show that the present day energy density in radions can be smaller than the closure density if the second inflationary epoch lasts about 8 e-foldings or more; the present-day radion mass turns out to be small (less than or of the order of an eV, depending on parameters). We argue that although our model envisages considerable time evolution in the Planck mass, substantial spatial fluctuations in Newton's constant are not produced.Comment: 38 pages, 2 figures, submitted to Phys Rev D. Typos corrected, references adde

Postpartum development of the mother-young relationship in goats

A first experiment was carried out to verify whether a goat may label her kid through licking and nursing in order to discriminate between her own and two alien kids. Furthermore, it was assessed how long after birth a kid needs to be along with its mother in order to be rejected by another goat and to be recognized by its own dam. All the 18 goats tested at 2 h accepted their own kid, whereas ten of them rejected both aliens; all the 20 goats tested at 4 h accepted their own young, whereas 17 rejected the alien isolated kid and 18 refused the alien labelled kid. In a second experiment physical contact, licking and nursing were prevented. All the 25 maternal goats accepted their own kids, whereas 11 of them rejected the alien. These two studies indicate that when the goat is left undisturbed with her kid after kidding, maternal selectivity is developed within 4 h

Stability of compactification during inflation

The possibility that inflation may trigger an instability in compactification of extra spatial dimensions is considered. In old, new, or extended inflation, the false vacuum energy results in a semiclassical instability in which the scalar field representing the radius of the extra dimensions may tunnel through a potential barrier leading to an expansion of the internal space. In chaotic inflation, if the initial value of the scalar field responsible for inflation is large enough, the internal space becomes classically unstable to ever increasing expansion. Restrictions on inflationary models necessary to keep the extra dimensions small are discussed. 15 refs., 5 figs