Spin-dependent transport through a chiral molecule in the presence of spin-orbit interaction and non-unitary effects

Recent experiments have demonstrated the efficacy of chiral helically shaped molecules in polarizing the scattered electron spin, an effect termed as chiral-induced spin selectivity (CISS). Here we solve a simple tight-binding model for electron transport through a single helical molecule, with spin-orbit interactions on the bonds along the helix. Quantum interference is introduced via additional electron hopping between neighboring sites in the direction of the helix axis. When the helix is connected to two one-dimensional single-mode leads, time-reversal symmetry prevents spin polarization of the outgoing electrons. One possible way to retrieve such a polarization is to allow leakage of electrons from the helix to the environment, via additional outgoing leads. Technically, the leakage generates complex site self-energies, which break unitarity. As a result, the electron waves in the helix become evanescent, with different decay lengths for different spin polarizations, yielding a net spin polarization of the outgoing electrons, which increases with the length of the helix (as observed experimentally). A maximal polarization can be measured at a finite angle away from the helix axis.Comment: 12 pages, 5 figure

The magnetic structure of the Jahn-Teller System LaTiO3

We investigate the effect of the experimentally observed Jahn-Teller distortion of the oxygen octahedra in LaTiO3 on the magnetic exchange. We present a localized model for the effective hopping between nearest-neighbor Ti ions and the intra-site Coulomb interactions, based on a non-degenerate orbital ground state due to the static crystal field. The latter corresponds to an orbital order which recently has been confirmed experimentally. Using perturbation theory we calculate, in addition to the Heisenberg coupling, antisymmetric and symmetric anisotropy terms of the superexchange spin Hamiltonian which are caused by the spin-orbit interaction. Employing our superexchange Hamiltonian, we deduce the magnetic order at low temperatures which is found to be in good agreement with experiment.Comment: 21 pages, 6 figure

The Potential for Carbon Sequestration in Agroforestry Systems

Potensi Agroforestri untuk Penyerapan Karbon. Sistem agroforestri memiliki potensi untuk mengatasi Perubahan lahan karena dapat menyerap karbon dan secara bersamaan memberikan keuntungan ekonomi kepada petani melalui berbagai produk-produk pertanian secara berkelanjutan. Sistem tersebut merupakan sistem penggunaan lahan terintegrasi yang terdiri dari berbagai pohon dan tumbuhan perenial berkayu lainnya yang tumbuh di lahan pertanian dan lahan produksi tahunan lainnya untuk memaksimalkan keuntungan ekonomi dari berbagai produk dan interaksi ekologi. Potensi agroforestri dalam penyerapan karbon sangat bervariasi tergantung pada beberapa faktor antara lain tipe sistem agroforestri yang digunakan, komposisi spesies, umur komponen spesies, lokasi geografis, faktor-faktor lingkungan dan praktek-praktek pengelolaan. Review literatur menunjukkan bahwa potensi penyerapan karbon dalam sistem agroforestry di daerah tropis berkisar dari 1,5 t C /ha/tahun sampai dengan 10 t C /ha/tahun, hamper sama dengan karbon yang diserap oleh hutan tanaman untuk pulp dan kertas yang sebesar 10 t C /ha/tahun. Di Sumberjaya, sebuah sistem agroforestri berbasis tanaman kopi diselidiki untuk mengetahui potensi sistem ini untuk penyerapan karbon. Hasil studi menunjukkan bahwa di survey pertama, rata-rata biomassa di kebun kopi umur 2-30 tahun adalah sekitar 92 Mg/ha. Survey kedua mengindikasikan bahwa rata-rata stok karbon dalam biomassa di atas tanah dari pohon kopi umur 6-40 tahun adalah 18,4 Mg/ha dengan standard deviasi 4,0, dan rata-rata stok karbon untuk pohon-pohon non-kopi adalah 29.6 Mg/ha dengan standar deviasi 18.9. Peningkatan stok karbon per tahun diperkirakan sebesar 2 Mg C/ha/tahun. Menghubungkan potensi agroforestri dalam penyerapan karbon dan Perubahan iklim akan memberikan insentif yang besar bagi petani-petani kecil di daerah tropis. Pemberian reward atau kompensasi kepada petani atas keuntungan lingkungan yang telah disediakan seperti pengurangan emisi akan membantu mengurangi kemiskinan di banyak areal pedesaan. Mengambil kesempatan dalam upaya mitigasi emisi karbon melalui sistem agroforestry juga dapat meningkatkan kapasitas negara berkembang seperti Indonesia untuk menghadapi Perubahan iklim

Measuring the Kondo effect in the Aharonov-Bohm interferometer

The conductance ${\cal G}$ of an Aharonov-Bohm interferometer (ABI), with a strongly correlated quantum dot on one arm, is expressed in terms of the dot Green function, $G_{dd}$, the magnetic flux $\phi$ and the non-interacting parameters of the ABI. We show that one can extract $G_{dd}$ from the observed oscillations of ${\cal G}$ with $\phi$, for both closed and open ABI's. In the latter case, the phase shift $\beta$ deduced from ${\cal G} \approx A+B\cos(\phi+\beta)$ depends strongly on the ABI's parameters, and usually $\beta \ne \pi/2$. These parameters may also reduce the Kondo temperature, eliminating the Kondo behavior

DNA Nanostructures as Smart Drug-Delivery Vehicles and Molecular Devices

Peer reviewe

Breakdown of `phase rigidity' and variations of the Fano effect in closed Aharonov-Bohm interferometers

Although the conductance of a closed Aharonov-Bohm interferometer, with a quantum dot on one branch, obeys the Onsager symmetry under magnetic field reversal, it needs not be a periodic function of this field: the conductance maxima move with both the field and the gate voltage on the dot, in an apparent breakdown of `phase rigidity'. These experimental findings are explained theoretically as resulting from multiple electronic paths around the interferometer ring. Data containing several Coulomb blockade peaks, whose shapes change with the magnetic flux, are fitted to a simple model, in which each resonant level on the dot couples to a different path around the ring

Order Parameters and Phase Diagram of Multiferroic \u3cem\u3eR\u3c/em\u3eMn\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e5\u3c/sub\u3e

The generic magnetic phase diagram of multiferroic RMn2O5 (with R = Y, Ho, Tb, Er, Tm), which allows different sequences of ordered magnetic structures for different R’s and different control parameters, is described using order parameters which explicitly incorporate the magnetic symmetry. A phenomenological magnetoelectric coupling is used to explain why some of these magnetic phases are also ferroelectric. Several new experiments, which can test this theory, are proposed

Was Superlocalization Observed in Carbon-Black–Polymer Composites?

A Comment on the Letter by van der Putten, Phys. Rev. Lett. 69, 494 (1992)

Assessment of Clinical Information: Comparison of the Validity of a Structured Clinical Interview (the Scid) and the Clinical Diagnostic Interview

Adaptive functioning is a key aspect of psychiatric diagnosis and assessment in research and practice. This study compared adaptive functioning validity ratings from Structured Clinical Interviews (SCIDs, symptom-focused structured diagnostic interviews), and Clinical Diagnostic Interviews (CDIs, systematic diagnostic interviews modeling naturalistic clinical interactions focusing on relational narratives). Two hundred forty-five patients (interviewed by two independent interviewers) and their interviewers completed the Clinical Data Form which assesses adaptive functioning and clinical information. Both interviews converged strongly with patient-reports, with no significant differences in validity of the interviews in measuring global and specific domains of adaptive functioning variables. Findings suggest that CDIs provide adaptive functioning data comparable to SCIDs (often considered gold standard for assessment but difficult to use in practice) and have important implications for bridging the research-practice gap. By incorporating clinicians\u27 everyday methods, CDIs yield information that is psychometrically sound for empirical investigation, diagnostically practical, and clinically meaningful and valid

Agreement Between Clinician and Patient Ratings of Adaptive Functioning and Developmental History

Objective: Psychiatric researchers rely heavily on patient report data for clinical research. However, patient reports are prone to defensive and self-presentation biases. Recent research using practice networks has relied on clinician reports, and both forensic and personality disorder researchers have recently turned to quantified data from clinically expert observers as well. However, critics have raised legitimate concerns about the reliability and validity of data from clinician informants. The aim of this study was to assess the validity and diagnostic efficiency of clinician reports of their patients\u27 adaptive functioning and developmental histories, using patient reports as the comparative standard traditionally used in psychiatric research. Method: Eighty-four clinicians and their patients completed a clinical data form designed to assess a range of patient functioning, clinical history, and developmental relationship variables used in multiple clinician report studies. The authors correlated clinician and patient reports across a number of clinically relevant adaptive functioning variables and calculated diagnostic efficiency statistics for a range of clinical history variables, including suicide attempts, hospitalizations, arrests, interpersonal conflicts affecting employment, and childhood physical and sexual abuse. Results: Across variables, patient-therapist correlations (0.40-0.66) and overall correct classification statistics (0.74-0.96) were high. Conclusions: The data demonstrate that clinicians\u27 judgments about their patients\u27 functioning and histories agree with patients\u27 self-reports and that in areas of discrepancy, clinicians tend to make appropriately conservative judgments in the absence of clear data. These findings suggest that quantified clinical judgment provides a vast untapped potential for large-sample research on psychopathology and treatment