Efficient Density Matrix Renormalization Group algorithm to study Y-Junctions with integer and half-integer spin

An efficient density matrix renormalization group (DMRG) algorithm is presented and applied to Y-junctions, systems with three arms of $n$ sites that meet at a central site. The accuracy is comparable to DMRG of chains. As in chains, new sites are always bonded to the most recently added sites and the superblock Hamiltonian contains only new or once renormalized operators. Junctions of up to $N = 3n + 1 \approx 500$ sites are studied with antiferromagnetic (AF) Heisenberg exchange $J$ between nearest-neighbor spins $S$ or electron transfer $t$ between nearest neighbors in half-filled Hubbard models. Exchange or electron transfer is exclusively between sites in two sublattices with $N_A \ne N_B$. The ground state (GS) and spin densities $\rho_r =$ at site $r$ are quite different for junctions with $S$ = 1/2, 1, 3/2 and 2. The GS has finite total spin $S_G = 2S (S)$ for even (odd) $N$ and for $M_G =S_G$ in the $S_G$ spin manifold, $\rho_r > 0 (< 0)$ at sites of the larger (smaller) sublattice. $S$ = 1/2 junctions have delocalized states and decreasing spin densities with increasing $N$. $S$ = 1 junctions have four localized $S_z = 1/2$ states at the end of each arm and centered on the junction, consistent with localized states in $S$ = 1 chains with finite Haldane gap. The GS of $S$ = 3/2 or 2 junctions of up to 500 spins is a spin density wave (SDW) with increased amplitude at the ends of arms or near the junction. Quantum fluctuations completely suppress AF order in $S$ = 1/2 or 1 junctions, as well as in half-filled Hubbard junctions, but reduce rather than suppress AF order in $S$ = 3/2 or 2 junctions.Comment: 11 pages, 11 Figures and submitted to PR

Regulation of cytoplasmic polyadenylation can generate a bistable switch

<p>Abstract</p> <p>Background</p> <p>Translation efficiency of certain mRNAs can be regulated through a cytoplasmic polyadenylation process at the pre-initiation phase. A translational regulator controls the polyadenylation process and this regulation depends on its posttranslational modifications e.g., phosphorylation. The cytoplasmic polyadenylation binding protein (CPEB1) is one such translational regulator, which regulates the translation of some mRNAs by binding to the cytoplasmic polyadenylation element (CPE). The cytoplasmic polyadenylation process can be turned on or off by the phosphorylation or dephosphorylation state of CPEB1. A specific example could be the regulation of Calcium/Calmodulin-dependent protein kinase II (αCaMKII) translation through the phosphorylation/dephosphorylation cycle of CPEB1.</p> <p>Result</p> <p>Here, we show that CPEB1 mediated polyadenylation of αCaMKII mRNA can result in a bistable switching mechanism. The switch for regulating the polyadenylation is based on a two state model of αCaMKII and its interaction with CPEB1. Based on elementary biochemical kinetics a high dimensional system of non-linear ordinary differential equations can describe the dynamic characteristics of the polyadenylation loop. Here, we simplified this high-dimensional system into approximate lower dimension system that can provide the understanding of dynamics and fixed points of original system. These simplified equations can be used to develop analytical bifurcation diagrams without the use of complex numerical tracking algorithm, and can further give us intuition about the parameter dependence of bistability in this system.</p> <p>Conclusion</p> <p>This study provides a systematic method to simplify, approximate and analyze a translation/activation based positive feedback loop. This work shows how to extract low dimensional systems that can be used to obtain analytical solutions for the fixed points of the system and to describe the dynamics of the system. The methods used here have general applicability to the formulation and analysis of many molecular networks.</p

Evaluation of Records of Oral and Maxillofacial Surgery Cases Reported at Abbasi Shaheed Hospital and Karachi Medical and Dental College, Pakistan

Background: Oral and Maxillofacial Surgery department is a diverse field in dentistry. Record maintenance has been established as one of the key factors in the success and integrity of health care institutes.Objective: The objective of the study was to evaluate the records of oral and maxillofacial surgery casesreported to oral and maxillofacial surgery department, Abbasi Shaheed Hospital and oral surgery OPD ofKarachi Medical and Dental College.Methods: Cross sectional study was conducted in at ASH and KMDC from July 2019 to September 2019.The data from January 2017 to July 2019 was retrospectively noted through electronic surgical recordof ASH and records of the Oral Surgery OPD of KMDC. Inclusion criteria was patients records of bothgenders of 5–70 years age, having complaint of any oral or dental pathology or pathologies, trauma andimpactions. Data was calculated manually by calculating frequencies and percentages for the trauma,impaction and pathology cases of patients.Results: In 2017, 239 cases were treated under general anesthesia from which trauma 11. 45% (n=11),followed by 48. 11% (n=115) cases of oral pathologies, total 11.7% (n=28) cases of complicated exodontias. In2018, among 211, 51.1% (n=108) cases were trauma followed by 39.3% (n=83) cases of oral pathologies,whereas, total 9.4% (n=20) complicated exodontias cases were observed. During 2019 (January to July),168 cases 36.2% (n=62) cases were diagnosed as trauma, in oral pathology, overall 36.2% (n=62) caseswere surgically excised. Total 23.2% (n=39) complicated exodontias. In 2017, 25122 cases were reported in Surgery OPD of Karachi Medical and Dental College. Total 36.2% (n=9097) teeth were extracted from which 1.93% (n=486) cases were surgical impaction. On the other hand, 1.65% (n=416) patients were treated through minor oral surgeries. In 2018, 29008 cases were reported in Surgery OPD. Total 42.7% (n=12377) teeth were extracted from which 0.92% (n=268) cases were surgical impaction. On the other hand, 0.71% (n=208) patients were treated through minor surgeries. In 2019, January till July 13028 cases were reported in Surgery OPD. Total42.6% (n=5559) teeth were extracted from which 0.66% (n=87) cases were surgical impaction. On the other hand, 0.68% (n=89) patients were treated through minor surgeries.Conclusion: It has been concluded that evaluation of the records of oral and maxillofacial surgery casesreported to oral and maxillofacial surgery department, Abbasi Shaheed Hospital and oral surgery OPD ofKarachi Medical and Dental College were high and appropriate measures should be taken in order tomanage these problems timely and effectively

Paspalum notatum Grass-waste-based Adsorbent for Rhodamine B Removal from Polluted Water

The potential of Paspalum notatum grass waste to adsorb Rhodamine B dye from aqueous phase is reported in this research. The grass waste was activated and characterized through various techniques to analyze the chemical (FTIR), morphological (SEMEDX), and thermal (TGA) changes incorporated through the activation process. The pollutant removal efficiency of the raw and modified adsorbents was studied by varying different process parameters in a batch process. The maximum capacity of adsorption which was observed for grass waste and activated grass waste was 54 mg g–1 and 72.4 mg g–1 respectively. Among the various kinetic models, the pseudo-second order model gives the best regression results. However, the intraparticle diffusion-adsorption model showed that the diffusion within pores controlled the adsorption rate. Thermodynamic analysis of this process revealed that Rhodamine B adsorption was endothermic and spontaneous in nature. The results of this study show that grass waste has the potential to be used as an adsorbent for the treatment of colored water. This work is licensed under a Creative Commons Attribution 4.0 International License

Kinetically controlled fabrication of gold nanorods and investigation of their thermal stability via in-situ TEM heating

Size controlled CTAB-capped AuNRs with various aspect ratios (ARs) ranging from 1.63±0.13 to 4.12±0.25 were synthesized following a modified seed-mediated method. Their thermal stability was examined by in-situ TEM heating. The results revealed a structural change from rods to spheres with increasing temperature. At lower temperatures 600ºC, particles became increasingly spherical. This behaviour occurred at temperatures lower than the melting point of bulk gold supporting a surface diffusion mechanism with material diffusing from the tips and redepositing at the middle of the rods. The rate of change in AR appeared to increase for thinner AuNRs