Density Matrix Perturbation Theory

An expansion method for perturbation of the zero temperature grand canonical density matrix is introduced. The method achieves quadratically convergent recursions that yield the response of the zero temperature density matrix upon variation of the Hamiltonian. The technique allows treatment of embedded quantum subsystems with a computational cost scaling linearly with the size of the perturbed region, O(N_pert.), and as O(1) with the total system size. It also allows direct computation of the density matrix response functions to any order with linear scaling effort. Energy expressions to 4th order based on only first and second order density matrix response are given.Comment: 4 pages, 2 figure

OC-163 identification of inflammatory bowel disease (IBD) using field asymmetric ion mobility spectrometry (FAIMS)

Introduction Resident colonic bacteria, principally anaerobes and firmicutes, ferment undigested fibre. The resultant volatile organic compounds (VOCs) formed are dissolved in the faeces but also absorbed and excreted in the urine. We have previously shown that electronic nose (E-nose) analysis of urine VOCs distinguishes between Crohn's disease (CD), ulcerative colitis (UC) and healthy volunteers (HV): the underlying principle is pattern recognition of disease-specific “chemical fingerprint”. High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) offers a possible alternative. The underlying principle is separation of VOC chemical components based on their different ion mobilties in high electric fields. We performed a pilot study in the above groups, the patients in remission (Rem) or with active disease (AD), to assess if this technology could achieve separation between the groups. The results were validated against E-nose analysis. Methods 59 subjects were studied; HV n=14, UC (Rem) n=18, UC (AD) n=4; CD (Rem) n=19, CD (AD) n=4. Urine samples (7 ml) in universal containers (25 ml) were heated to 40±0.1 C. The headspace (the air above the sample) was then analysed using FAIMS. The data were analysed by Fisher Discriminant Analysis. Results The technique distinguished between the three groups. Additionally, patients with active disease could be distinguished from those in remission. These results were concordant with E-nose analysis. Conclusion This pilot shows that urine VOCs, analysed by the different approaches of E-nose and FAIMS, the latter a novel application, can distinguish the healthy from those with UC and CD when disease is active or in remission. The two technologies together offer a non-invasive approach to diagnosis and follow-up in inflammatory bowel disease

Theoretical Study of Physisorption of Nucleobases on Boron Nitride Nanotubes: A New Class of Hybrid Nano-Bio Materials

We investigate the adsorption of the nucleic acid bases, adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U) on the outer wall of a high curvature semiconducting single-walled boron nitride nanotube (BNNT) by first principles density functional theory calculations. The calculated binding energy shows the order: G>A\approxC\approxT\approxU implying that the interaction strength of the (high-curvature) BNNT with the nucleobases, G being an exception, is nearly the same. A higher binding energy for the G-BNNT conjugate appears to result from a stronger hybridization of the molecular orbitals of G and BNNT, since the charge transfer involved in the physisorption process is insignificant. A smaller energy gap predicted for the G-BNNT conjugate relative to that of the pristine BNNT may be useful in application of this class of biofunctional materials to the design of the next generation sensing devices.Comment: 17 pages 6 figure

The detection of patients at risk of gastrointestinal toxicity during pelvic radiotherapy by electronic nose and FAIMS : a pilot study

It is well known that the electronic nose can be used to identify differences between human health and disease for a range of disorders. We present a pilot study to investigate if the electronic nose and a newer technology, FAIMS (Field Asymmetric Ion Mobility Spectrometry), can be used to identify and help inform the treatment pathway for patients receiving pelvic radiotherapy, which frequently causes gastrointestinal side-effects, severe in some. From a larger group, 23 radiotherapy patients were selected where half had the highest levels of toxicity and the others the lowest. Stool samples were obtained before and four weeks after radiotherapy and the volatiles and gases emitted analysed by both methods; these chemicals are products of fermentation caused by gut microflora. Principal component analysis of the electronic nose data and wavelet transform followed by Fisher discriminant analysis of FAIMS data indicated that it was possible to separate patients after treatment by their toxicity levels. More interestingly, differences were also identified in their pre-treatment samples. We believe these patterns arise from differences in gut microflora where some combinations of bacteria result to give this olfactory signature. In the future our approach may result in a technique that will help identify patients at “high risk” even before radiation treatment is started

Physisorption of Nucleobases on Graphene

We report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with graphene, carried out within the density functional theory framework, with additional calculations utilizing Hartree--Fock plus second-order Moeller-Plesset perturbation theory. The calculated binding energy of the nucleobases shows the following hierarchy: G > T ~ C ~ A > U, with the equilibrium configuration being very similar for all five of them. Our results clearly demonstrate that the nucleobases exhibit significantly different interaction strengths when physisorbed on graphene. The stabilizing factor in the interaction between the base molecule and graphene sheet is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study represents a significant step towards a first-principles understanding of how the base sequence of DNA can affect its interaction with carbon nanotubes, as observed experimentally.Comment: 7 pages, 3 figure

Penggunaan Metode Semiempirik AM1 Untuk Pemilihan Monomer Fungsional Efektif Pada Prasintesis Polimer Tercetak Diazinon

Pemilihan monomer fungsional yang efektif untuk sintesis Molecular Imprinted Polymer (MIP)untuk diazinon dapat dilakukan dengan pendekatan kimia komputasi dengan menerapkan metode semiempirik AM1. Proses seleksi menggunakan parametermomen dipol, energi interaksi, dan ikatan hidrogen yang terbentuk. Energi interaksi yang optimum menunjukkan kompleks yang terbentuk stabildan mengindikasikan MIP akan dapat terbentuk baik.Semua perhitungan pada penelitian ini dilakukan dengan menggunakan software Hyperchem 7.5. Hasil penelitian menunjukkan monomer fungsional efektif untuk prasintesis polimer tercetak diazinon yaitu akrilamida, asam akrilat, asam metakrilat, hidroksi etil metakrilat, asam urokanat, asam itakonat, dan asam urokanat etil ester. Hasil ini secara teoritik dapat memberikan informasi mengenai monomer fungsional efektif yang dapat digunakan sebagai pertimbangan sintesis MIP untuk diazinon dengan selektivitas relatif baik

ISOLASI DAN SELEKSI BAKTERI PENGHASIL ENZIM EKSTRASELULER PADA TANAH MANGROVE DI PANTAI NOELBAKI

Bakteri yang hidup pada tanah mangrove bersifat halofilik yaitu mampu hidup pada lingkungan dengan kondisi kadar garam yang tinggi. Bakteri yang hidup pada zona yang ekstrim memerlukan protein yang tinggi untuk mempertahankan hidup dan dapat melakukan metabolisme, salah satunya dengan membentuk enzim terutama enzim ekstra seluler (enzim amilase, protease, selulase dan lipase). Tujuannya yaitu untuk mengisolasi dan menyeleksi bakteri penghasil enzim ekstraseluler. Metode yang digunakan adalah survey dan eksperimental terhadap isolasi bakteri dari tanah mangrove yang dikarakterisasi berdasarkan morfologi, pewarnaan gram, dan uji aktivitas enzim amilase dengan media amilum, protease dengan media skim milk, selulase dengan media Carboxy Methyl Cellulosed an lipase dengan media tween 80. Analisis data secara deskriptif kuantitatif. Terdapat tiga parameter yang diukur yaitu suhu, salinitas dan pH. Berdasarkan data penelitian ditemukan bahwa tanah mangrove yang ada di pantai Noelbaki menghasilkan 70 isolat bakteri penghasil enzim ekstra seluler. 33 isolat bakteri memiliki aktifitas enzim amilase, 20 isolat memiliki aktifitas enzim proteolitik, 56 isolat memiliki aktifitas selulolitik,10 isolat memiliki aktifitas lipolitik, sehingga total isolat yang memproduksi enzim ekstraseluler adalah 119 isolat, hal ini menjelaskan bahwa beberapa isolat memiliki kemampuan menghasilkan enzim multi-aktifitas atau mampu menghasilkan beberapa enzim.ISOLATION AND SELECTION OF BACTERIA PRODUCING EXTRACELLULAR ENZYMES ON MANGROVE LAND OF NOELBAKI BEACH. Bacteria living in the halofilic mangrove land are able to live in environments that are high salinity. Bacteria that live in the extreme zone require high proteins to sustain life and can metabolize, one by forming enzymes especially extra-cellular enzymes (amilase, protease, selulase and lipase). The aim was to isolate and select extra-cellular enzyme bacteria. This method was a survey and experimental against the insulation of mangrove land controlled by morphology, dyeing grams, and testing for amilase enzyme activity for amilum media, protease with skim milk, selulase with medium carboxy methyl cellulose and lipase in tween media. Quantitative descriptive analysis of data. Three parameters, measured temperature, salinity and ph. Based on research data, were found that mangrove soils located on the coast of noelbaki produced 70 insulations of extreme enzyme yielding bacteria. 33 bacterial isolates have activity in amilase enzyme, 20 isolates have protein activity, 56 isolates had activity cellulase enzyme, 10 isolates had activities lipase enzyme, that include 119 isolates which produced extra-cellular enzymes, which made it clear that some isolates had the ability to create a multi-activity enzyme

Highly efficient (Cs8V) superatom-based spin-polarizer

Quantum transport through molecules and the possibility to manipulate spin has generated tremendous excitement. Here, we demonstrate unusual spin transport through a molecule of twoCs8V magnetic superatoms. Calculations based on density functional theory and nonequilibrium Green’s function methods find a much higher current for the spin-down charge carriers relative to the spin-up carriers in the model Au–(Cs8V)–(Cs8V)–Au device system with almost 100% spin polarization, indicating a highly efficient spin polarizer. The new behavior is rooted in strong coupling of the localized magnetic core on V and the itinerant electrons of the Cs shell atoms leading to nearly full spin polarization