Quantum Evaporation from Superfluid Helium at Normal Incidence

We study the scattering of atoms, rotons and phonons at the free surface of $^4$He at normal incidence and calculate the evaporation, condensation and reflection probabilities. Assuming elastic one-to-one processes and using general properties of the scattering matrix, such as unitarity and time reversal, we argue that all nonzero probabilities can be written in terms of a single energy-dependent parameter. Quantitative predictions are obtained using linearized time dependent density functional theory.Comment: 12 pages, REVTeX, 2 postscript figures, available also at http://anubis.science.unitn.it/~dalfovo/papers/papers.htm

Penyempurnaan Kecerdasan Emosional Dalam Pendidikan Islam Untuk Anak Remaja Melalui Kegiatan Spiritualitas (Didikan Shubuh)

Menurut Cooper dan Sawaf (1999), kecerdasan emosi adalah kemampuan merasakan,memahami dan secara efektif menerapkan daya dan kepekaan emosi sebagai sumber energy, informasi, koreksi dan pengaruh yang manusiawi. Pendidikan Islam sangat tepat dalam memengaruhi emosional para remaja kearah yang lebih baik dan bisa mengendalikan apa yang akan dipikirkan , diucapkan , dan lalu diperbuat. Hal ini dilakukan demi kebaikan remaja sehingga mereka tidak terjerumus ke hal yang bathil. Dengan kegiatan seperti Majlis Remaja Islam, pelaksanaan kegiatan didikan subuh , remaja lebih terarah dalam kesehariannya, bermanfaat bagi lingkungan masyarakat, keluarga, dan diri pribadi mereka. Ilmu yang didapat seperti pengayaan makna dalam Al-Quran dan Hadist ,kegiatan kesenian seperti syair dan berbagai musyawarah yang dilakukan untuk kegiatan sosial kemasyarakatan lainnya. Spiritualitas bagi para remaja dibutuhkan agar dapat membentengi diri dari tindakan maksiat dan lebih kurang meminimalisir segala bentuk penyimpangan yang ada di kehidupan mereka sehari-hari karena pemikiran dunia ini hanya sementara dan akhirat kekal untuk selamanya menjadi moto bagi kita untuk hidup secara seimbang dan tidak melalaikan dan melebihkan diantara keduanya

Rotons and Quantum Evaporation from Superfluid 4He

The probability of evaporation induced by $R^+$ and $R^-$ rotons at the surface of superfluid helium is calculated using time dependent density functional theory. We consider excitation energies and incident angles such that phonons do not take part in the scattering process. We predict sizable evaporation rates, which originate entirely from quantum effects. Results for the atomic reflectivity and for the probability of the roton change-mode reflection are also presented.Comment: 11 pages, REVTEX, 3 figures available upon request or at http://anubis.science.unitn.it/~dalfovo/papers/papers.htm

POLA PEMETAAN PENYEBARAN PENYAKIT DEMAM BERDARAH PADA WILAYAH KOTA PALEMBANG

Palembang region consists of 16 districts, an area that is separated by a large river that divides into two regionsand Ulu Ilir, Palembang, besides most of the region is also an area of swamps. Environmental conditions is very large influence on the spread of dengue fever. The problem faced is the difficulty of mapping the spread of dengue fever that has slowed the anticipation and prevention of dengue fever cases. Needed a pattern that maps the spread of dengue fever by location (region), time, and season. To prevent Extraordinary Events (KLB) and monitor the spread of dengue fever in the region of Palembang in this study carried out to map the spread of dengue fever in the region of Palembang by using the nearest neighbor method

Density functional calculations for 4He droplets

A novel density functional, which accounts correctly for the equation of state, the static response function and the phonon-roton dispersion in bulk liquid helium, is used to predict static and dynamic properties of helium droplets. The static density profile is found to exhibit significant oscillations, which are accompanied by deviations of the evaporation energy from a liquid drop behaviour in the case of small droplets. The connection between such oscillations and the structure of the static response function in the liquid is explicitly discussed. The energy and the wave function of excited states are then calculated in the framework of time dependent density functional theory. The new functional, which contains backflow-like effects, is expected to yield quantitatively correct predictions for the excitation spectrum also in the roton wave-length range.Comment: 15 pages, REVTEX, 10 figures available upon request or at http://anubis.science.unitn.it/~dalfovo/papers/papers.htm

Dispersion of Ripplons in Superfluid 4he

A detailed study of the dispersion law of surface excitations in liquid \hef at zero temperature is presented, with special emphasis to the short wave length region. The hybridization mechanism between surface and bulk modes is discussed on a general basis, investigating the scattering of slow rotons from the surface. An accurate density functional, accounting for backflow effects, is then used to determine the dispersion of both bulk and surface excitations. The numerical results are close to the experimental data obtained on thick films and explicitly reveal the occurrence of important hybridization effects between ripplons and rotons.Comment: 23 pages, REVTEX 3.0, 11 figures upon request, UTF-326/9

Bose-Einstein Condensation at a Helium Surface

Path Integral Monte Carlo was used to calculate the Bose-Einstein condensate fraction at the surface of a helium film at $T=0.77 K$, as a function of density. Moving from the center of the slab to the surface, the condensate fraction was found to initially increase with decreasing density to a maximum value of 0.9 before decreasing. Long wavelength density correlations were observed in the static structure factor at the surface of the slab. Finally, a surface dispersion relation was calculated from imaginary-time density-density correlations.Comment: 8 pages, 5 figure

Structural and dynamical properties of superfluid helium: a density functional approach

We present a novel density functional for liquid 4He, properly accounting for the static response function and the phonon-roton dispersion in the uniform liquid. The functional is used to study both structural and dynamical properties of superfluid helium in various geometries. The equilibrium properties of the free surface, droplets and films at zero temperature are calculated. Our predictions agree closely to the results of ab initio Monte Carlo calculations, when available. The introduction of a phenomenological velocity dependent interaction, which accounts for backflow effects, is discussed. The spectrum of the elementary excitations of the free surface and films is studied.Comment: 37 pages, REVTeX 3.0, figures on request at [email protected]