Charging induced asymmetry in molecular conductors

We investigate the origin of asymmetry in various measured current-voltage (I-V) characteristics of molecules with no inherent spatial asymmetry, with particular focus on a recent break junction measurement. We argue that such asymmetry arises due to unequal coupling with the contacts and a consequent difference in charging effects, which can only be captured in a self-consistent model for molecular conduction. The direction of the asymmetry depends on the sign of the majority carriers in the molecule. For conduction through highest occupied molecular orbitals (i.e. HOMO or p-type conduction), the current is smaller for positive voltage on the stronger contact, while for conduction through lowest unoccupied molecular orbitals (i.e. LUMO or n-type conduction), the sense of the asymmetry is reversed. Within an extended Huckel description of the molecular chemistry and the contact microstructure (with two adjustable parameters, the position of the Fermi energy and the sulphur-gold bond length), an appropriate description of Poisson's equation, and a self-consistently coupled non-equilibrium Green's function (NEGF) description of transport, we achieve good agreement between theoretical and experimental I-V characteristics, both in shape as well as overall magnitude.Comment: length of the paper has been extended (4 pages to 6 pages), two new figures have been added (3 figures to 5 figures), has been accepted for PR

Variasi Spasio-temporal Jenis Makanan Ikan Motan, Thynnichthys Polylepis Di Rawa Banjiran Sungai Kampar Kiri, Riau [Spatio-temporal Variation in the Diet of Thynnichtys Polylepis in Floodplain River of Kampar Kiri, Riau]

The research aimed to describe diet composition of Thynnichthyes polylepis. The diet compositions of population from two sites (Mentulik and Simalinyang) in floodplain river of Kampar Kiri, were compared according to the month. Fishes were captured using experimental gillnet and trap. For food habits analysis, the index of preponderance method was used. The collections were performed monthly from July to December 2008, where the stomach contents of 479 specimens were assessed. Prey items of T. polylepis were basically composed of phytoplankton and zooplankton, especially Cocconeis, Nitzschia, Navicula, Cyclotella, Pleurotaenium, and Testudinella. At site Mentulik, the most common items were Cocconeis, Nitzschia, and Navicula. Conversely, at site Simalinyang, Cocconeis, Pleurotaenium, and Nitzschia more representative. In general, main food of fish origin showed the highest index values at Mentulik, whereas at Simalinyang. The composition of items varied monthly, especially at Simalinyang. Food habits of fish may be flexible according to resource availability in spatial and temporal variation

Oocyte Development of Scalloped Perchlet, Ambassis Nalua (Hamilton 1822)

Ikan seriding (Ambassis nalua) merupakan salah satu jenis ikan di perairan Teluk Pabean, Indramayu yang berukuran kecil, transparan dan tersedia dalam jumlah melimpah. Penelitian ini bertujuan untuk melihat perkembangan sel telur secara histologis dan menentukan tipe pemijahan ikan seriding. Ikan seriding didapatkan dari hasil tangkapan nelayan di Teluk Pabean, kemudian gonad contoh diawetkan dengan menggunakan larutan BNF (Buffer Neutral Formalin). Preparat histo-logis sel telur dibuat dengan metode pewarnaan HE, kemudian diamati dibawah mikroskop berkamera. Tahapan perkembangan oosit pada ikan seriding yaitu kromatin nukleus dan perinuklear (tahap pertumbuhan awal), kortikal alveoli, vitelo-genesis, dan pematangan. Tahapan tersebut menunjukkan bahwa ikan seriding merupakan tipe ikan yang memijah secara bertahap

Reproductive Aspects Of Scalloped Perchlet, Ambassis Nalua (Hamilton, 1822) In Pabean Bay Indramayu, West Java

Scalloped perchlet, Ambassis nalua, is one of fishes in Pabean Bay, Indramayu. This research aims to determine the reproductive aspects of Ambassis nalua in Pabean Bay Indramayu including sex ratio, spawning season, first maturity, fecundity and spawning pattern. Fish samples were collected by trap net and trammel net at three sites in Pabean Bay from April to October 2015. A total of 424 of A. nalua were caught, consist of 114 males and 310 females; with total length ranged from 38.04 to 112.63 mm and total weight ranged from 0.37 to 25.44 g. Sex ratio of mature fish was 1:1.9. The mature males and females were found in every month of sampling period. The gonado-somatic index (GSI) ranged from 0.40 to 0.83 and 2.36 to 4.54 for male and female, respectively. The peak of spawning season was found in September. The first maturity (Lm50) for male and female were 79.17 mm and 91.25 mm, respectively. The fecundity varied from 3,451–32,465 eggs. Egg diameter distribution shows that spawning pattern of A. nalua was batch spawner

Incoherent Transport through Molecules on Silicon in the vicinity of a Dangling Bond

We theoretically study the effect of a localized unpaired dangling bond (DB) on occupied molecular orbital conduction through a styrene molecule bonded to a n++ H:Si(001)-(2x1) surface. For molecules relatively far from the DB, we find good agreement with the reported experiment using a model that accounts for the electrostatic contribution of the DB, provided we include some dephasing due to low lying phonon modes. However, for molecules within 10 angstrom to the DB, we have to include electronic contribution as well along with higher dephasing to explain the transport features.Comment: 9 pages, 5 figure

Oxygen vacancy filament formation in TiO 2: A kinetic Monte Carlo study

We report a kinetic Monte Carlo (kMC) investigation of an atomistic model for 3-dimensional structural configurations of TiO 2 memristor, focusing on the oxygen vacancy migration and interaction under an external voltage bias. kMC allows the access of experimental time scales so that the formation of well defined vacancy filaments in thin TiO 2 films can be simulated. The results show that the electric field drives vacancy migration; and vacancy hopping-induced localized electric field plays a key role for the filament evolution. Using the kMC structure of the filaments at different stages of the formation process, electronic density of states (DOS) are calculated by density functional theory. Filament induced gap states are found which gives rise to a transition from insulating behavior to conducting behavior during the filament formation process. By varying kMC simulations parameters, relations between vacancy diffusion, filament formation, and DOS in the TiO 2 thin film are elucidated. © 2012 American Institute of Physics.published_or_final_versio

The D153del mutation in GNB3 gene causes tissue specific signalling patterns and an abnormal renal morphology in rge chickens

Background The GNB3 gene is expressed in cone but not rod photoreceptors of vertebrates, where it acts as the β transducin subunit in the colour visual transduction process. A naturally occurring mutation ‘D153del’ in the GNB3 gene causes the recessively inherited blinding phenotype retinopathy globe enlarged (rge) disease in chickens. GNB3 is however also expressed in most other vertebrate tissues suggesting that the D153del mutation may exert pathological effects that outlie from eye. Principal Findings Recombinant studies in COS-7 cells that were transfected with normal and mutant recombinant GNB3 constructs and subjected to cycloheximide chase showed that the mutant GNB3d protein had a much shorter half life compared to normal GNB3. GNB3 codes for the Gβ3 protein subunit that, together with different Gγ and Gα subunits, activates and regulates phosphorylation cascades in different tissues. As expected, the relative levels of cGMP and cAMP secondary messengers and their activated kinases such as MAPK, AKT and GRK2 were also found to be altered significantly in a tissue specific manner in rge chickens. Histochemical analysis on kidney tissue sections, from rge homozygous affected chickens, showed the chickens had enlargement of the glomerular capsule, causing glomerulomegaly and tubulointerstitial inflammation whereas other tissues (brain, heart, liver, pancreas) were unaffected. Significance These findings confirm that the D153del mutation in GNB3 gene targets GNB3 protein to early degradation. Lack of GNB3 signalling causes reduced phosphorylation activity of ERK2 and AKT leading to severe pathological phenotypes such as blindness and renal abnormalities in rge chickens

A Fuzzy Approach for Feature Evaluation and Dimensionality Reduction to Improve the Quality of Web Usage Mining Results

The explosive growth in the information available on the Web has necessitated the need for developing Web personalization systems that understand user preferences to dynamically serve customized content to individual users. Web server access logs contain substantial data about the accesses of users to a Web site. Hence, if properly exploited, the log data can reveal useful information about the navigational behaviour of users in a site. In order to reveal the information about user preferences from, Web Usage Mining is being performed. Web Usage Mining is the application of data mining techniques to web usage log repositories in order to discover the usage patterns that can be used to analyze the user’s navigational behavior. WUM contains three main steps: preprocessing, knowledge extraction and results analysis. During the preprocessing stage, raw web log data is transformed into a set of user profiles. Each user profile captures a set of URLs representing a user session. Clustering can be applied to this sessionized data in order to capture similar interests and trends among users’ navigational patterns. Since the sessionized data may contain thousands of user sessions and each user session may consist of hundreds of URL accesses, dimensionality reduction is achieved by eliminating the low support URLs. Very small sessions are also removed in order to filter out the noise from the data. But direct elimination of low support URLs and small sized sessions may results in loss of a significant amount of information especially when the count of low support URLs and small sessions is large. We propose a fuzzy solution to deal with this problem by assigning weights to URLs and user sessions based on a fuzzy membership function. After assigning the weights we apply a "Fuzzy c-Mean Clustering" algorithm to discover the clusters of user profiles. In this paper, we describe our fuzzy set theoretic approach to perform feature selection (or dimensionality reduction) and session weight assignment. Finally we compare our soft computing based approach of dimensionality reduction with the traditional approach of direct elimination of small sessions and low support count URLs. Our results show that fuzzy feature evaluation and dimensionality  reduction results in better performance and validity indices for the discovered clusters