Self-T-Dual Brane Cosmology and the Cosmological Constant Problem

We consider a codimension-one brane embedded in a gravity-dilaton bulk action, whose symmetries are compatible with T-duality along the space-like directions parallel to the brane, and the bulk time-like direction. The equations of motions in the string frame allow for a smooth background obtained by the union of two symmetric patches of AdS space. The Poincar\'{e} invariance of the solution appears to hold independently of the value of the brane vacuum energy, through a self-tuning property of the dilaton ground state. Moreover, the effective cosmology displays a bounce, at which the scale factor does not shrink to zero. Finally, by exploiting the T-duality symmetry, we show how to construct an ever-expanding Universe, along the lines of the Pre-Big Bang scenario.Comment: Minor corrections, comments & references added. Accepted for publicatio

A momentum-space representation of Green's functions with modified dispersion on ultra-static space-time

We consider the Green's functions associated to a scalar field propagating on a curved, ultra-static background, in the presence of modified dispersion relations. The usual proper-time deWitt-Schwinger procedure to obtain a series representation of the Green's functions is doomed to failure, because of higher order spatial derivatives in the Klein-Gordon operator. We show how to overcome this difficulty by considering a preferred frame, associated to a unit time-like vector. With respect to this frame, we can express the Green's functions as an integral over all frequencies of a space-dependent function. The latter can be expanded in momentum space, as a series with geometric coefficients similar to the deWitt-Schwinger's ones. By integrating over all frequencies, we finally find the expansion of the Green's function up to four derivatives of the metric tensor. The relation with the proper-time formalism is also discussed.Comment: revtex, version accepted for publication in Phys. Rev.

The Electronic Nature of the 1,4-β-Glycosidic Bond and Its Chemical Environment: DFT Insights into Cellulose Chemistry

The molecular understanding of the chemistry of 1,4-β-glucans is essential for designing new approaches to the conversion of cellulose into platform chemicals and biofuels. In this endeavor, much attention has been paid to the role of hydrogen bonding occurring in the cellulose structure. So far, however, there has been little discussion about the implications of the electronic nature of the 1,4-β-glycosidic bond and its chemical environment for the activation of 1,4-β-glucans toward acid-catalyzed hydrolysis. This report sheds light on these central issues and addresses their influence on the acid hydrolysis of cellobiose and, by analogy, cellulose. The electronic structure of cellobiose was explored by DFT at the BB1 K/6-31++G(d,p) level. Natural bond orbital (NBO) analysis was performed to grasp the key bonding concepts. Conformations, protonation sites, and hydrolysis mechanisms were examined. The results for cellobiose indicate that cellulose is protected against hydrolysis not only by its supramolecular structure, as currently accepted, but also by its electronic structure, in which the anomeric effect plays a key role

Bandgap Narrowing in Quantum Wires

In this paper we consider two different geometry of quasi one-dimensional semiconductors and calculate their exchange-correlation induced bandgap renormalization (BGR) as a function of the electron-hole plasma density and quantum wire width. Based on different fabrication scheme, we define suitable external confinement potential and then leading-order GW dynamical screening approximation is used in the calculation by treating electron-electron Coulomb interaction and electron-optical phonon interaction. Using a numerical scheme, screened Coulomb potential, probability of different states, profile of charge density and the values of the renormalized gap energy are calculated and the effects of variation of confinement potential width and temperature are studied.Comment: 17 Pages, 4 Figure

Penerapan Secret Sharing Scheme Pada Joint Ownership Watermarking Untuk Citra Digital

Digital watermarking merupakan metode untuk menyisipkan suatu informasi, yangbiasanya disebut sebagai watermark, pada suatu data digital penampung. Masalah yangdihadapi pada metode digital watermarking saat ini adalah semua metode yang telah adahanya mampu menangani perlindungan hak cipta dari satu pemilik saja. Solusi yangkemudian ditawarkan untuk menangani masalah kepemilikan bersama suatu citra digitaladalah dengan menerapkan secret sharing scheme pada digital image watermarking.Makalah ini membahas tentang penerapan secret sharing scheme pada joint ownershipwatermarking yang meliputi protokol-protokol dan metode-metode untuk proses penyisipan(embedding) watermark serta protokol-protokol untuk proses pendeteksian kepemilikan(detection) watermark. Robustness watermark diuji dengan melakukan beberapa prosesmanipulasi terhadap citra digital yang telah mengandung watermark, kemudian dilakukanproses pendeteksian kepemilikan watermark terhadap citra digital tersebut. Hasil ujimenunjukkan, watermark cukup robust terhadap beberapa proses manipulasi citra digital,seperti Perubahan brightness, kontras, scaling, flipping, rotasi, printscreen, serta kompresiJPEG 2000. Namun watermark masih rentan terhadap proses cropping dan penyisipanwatermark ganda pada citra digital

Exploiting exciton-exciton interactions in semiconductor quantum dots for quantum-information processing

We propose an all-optical implementation of quantum-information processing in semiconductor quantum dots, where electron-hole excitations (excitons) serve as the computational degrees of freedom (qubits). We show that the strong dot confinement leads to an overall enhancement of Coulomb correlations and to a strong renormalization of the excitonic states, which can be exploited for performing conditional and unconditional qubit operations.Comment: 5 pages revtex, 2 encapsulated postscript figures. Accepted for publication in Phys. Rev. B (Rapid Communication

Experimental Validation of the Innovative Thermal Energy Storage Based on an Integrated System "Storage Tank/Steam Generator"

Abstract In the past years, an innovative thermal energy storage system at high temperature (up to 550C) for CSP plants was proposed by ENEA and Ansaldo Nucleare: a single storage tank integrated with a steam generator immersed in the heat storage medium. The idea is based on the exploitation of the thermophysical characteristics of the heat storage medium (a binary mixture of salts of NaNO3 at 60% and KNO3 at 40%) in order to maintain over time, in the single tank, a thermal stratification of the fluid. The thermal stratification is able to trigger, in the immersed steam generator, the natural circulation, shell side and downwards, of the hot molten salt cooled down by the water that flows upwards tube side, thus heating up and producing superheated steam. The advantages of such a system are: - efficient performances; - simple implementation; - compactness: - modularity; - and, overall, contained costs: only one storage tank instead of the two tanks and only one heat exchanger instead of the three exchangers of the classic configuration; reduced quantity of salt; minimization of piping, valves and other components. The technical feasibility of the proposed system, together with the stability over time of the stratification in temperature of the storage medium, have been already verified and assessed. This report has the aim of presenting the experimental results obtained by ENEA in the Casaccia Research Centre (Rome, Italy), with a small scale test section consisting of a 300 kWth steam generator inserted in a 8 m3 storage tank with molten salt at high temperature. The reported results relate to the behaviour of the system in steady state conditions, and show its promising performances

Pengelolaan Lahan Kelapa Sawit dalam Meningkatkan Pendapatan Kelompok Plasma di Serawai

This research aims to determine how the land management of oil palm farmers in increasing the income of farmers in the village of Nanga Serawai plasma. The method used is descriptive method with the form of case study research. With a population of 25 farmers and the total sample of 25 farmers. Data collection techniques used are direct observation techniques, communication techniques directly, indirect communication techniques and engineering documentation with data collection tools such as observation, interview, document and book remarks. The results of this study are as follows: (1) Management of the plasma is carried out by farmers is good enough. (2) Based on the data obtained from the study of the views of the plasma pendapaan after managing quite well. (3) Barriers can be obtained by farmers ditangulangi by changing the schedule departure, how in good enough so i can always keep farmers and land mengelolan plasma

Factors Associated with Physical Frailty in Elderly Women with Low Socioeconomic Status in Urban Communities: A Cross-Sectional Study

Background: there are differences in factors associated with frailty syndrome in elderly population. The aim of this research was to determine frailty status (fit, pre-frail and frail) and to identify factors associated with physical frailty in urban community-dwelling elderly women. Methods: a cross-sectional study of community-dwelling women aged 60 years and older was conducted in West and Central Jakarta regions, Indonesia, from July until September 2017. The Cardiovascular Health Study (CHS) score was used to determine frailty status (fit/ pre-frail/ frail). Chi-Square Test and logistic regression analysis were used to determine association between independent variables and physical frailty. Results: there were 325 female subjects with a median age of 67 (60–94) years; 95.7% had income below the Provincial Minimum Income of DKI Jakarta in 2017 (<3.3 million IDR≈238 USD/month), and 92.6% had a level of education ≤9 years. Subjects were classified into this following groups: fit (12.6%), pre-frail (63.4%) and frail (24%). Factors associated with physical frailty were age above 70 years old with OR 5.27, lower Barthel Index for Activities of Daily Living (B-ADL) with OR 2.85, depressive symptoms with OR 6.79, and Euro Quality of Life-5 Dimensions (EQ-5D) index with OR 1.96. Conclusion: elderly women in the urban community with low socioeconomic status were classified as fit (12.6%), pre-frail (63.4%) and frail (24%). Factors associated with physical frailty were age above 70 years old, depressive symptoms, lower functional status and health-related quality of life index