Confinement-Deconfinement Transition as an Indication of Spin-Liquid-Type Behavior in Na2_2IrO3_3

We use ultrafast optical spectroscopy to observe binding of charged single-particle excitations (SE) in the magnetically frustrated Mott insulator Na$_2$IrO$_3$. Above the antiferromagnetic ordering temperature ($T_N$) the system response is due to both Hubbard excitons (HE) and their constituent unpaired SE. The SE response becomes strongly suppressed immediately below $T_N$. We argue that this increase in binding energy is due to a unique interplay between the frustrated Kitaev and the weak Heisenberg-type ordering term in the Hamiltonian, mediating an effective interaction between the spin-singlet SE. This interaction grows with distance causing the SE to become trapped in the HE, similar to quark confinement inside hadrons. This binding of charged particles, induced by magnetic ordering, is a result of a confinement-deconfinement transition of spin excitations. This observation provides evidence for spin liquid type behavior which is expected in Na$_2$IrO$_3$.Comment: 5 pages, 3 figure

The origin of exciton mass in a frustrated Mott insulator Na2_2IrO3_3

We use a three-pulse ultrafast optical spectroscopy to study the relaxation processes in a frustrated Mott insulator Na$_2$IrO$_3$. By being able to independently produce the out-of-equilibrium bound states (excitons) of doublons and holons with the first pulse and suppress the underlying antiferromagnetic order with the second one, we were able to elucidate the relaxation mechanism of quasiparticles in this system. By observing the difference in the exciton dynamics in the magnetically ordered and disordered phases we found that the mass of this quasiparticle is mostly determined by its interaction with the surrounding spins

Fluctuating charge density waves in a cuprate superconductor

Cuprate materials hosting high-temperature superconductivity (HTS) also exhibit various forms of charge and/or spin ordering whose significance is not fully understood. To date, static charge-density waves (CDWs) have been detected by diffraction probes only at special doping or in an applied external field. However, dynamic CDWs may also be present more broadly and their detection, characterization and relationship with HTS remain open problems. Here, we present a new method, based on ultrafast spectroscopy, to detect the presence and measure the lifetimes of CDW fluctuations in cuprates. In an underdoped La1.9Sr0.1CuO4 film (Tc = 26 K), we observe collective excitations of CDW that persist up to 100 K. This dynamic CDW fluctuates with a characteristic lifetime of 2 ps at T = 5 K which decreases to 0.5 ps at T = 100 K. In contrast, in an optimally doped La1.84Sr0.16CuO4 film (Tc = 38.5 K), we detect no signatures of fluctuating CDWs at any temperature, favoring the competition scenario. This work forges a path for studying fluctuating order parameters in various superconductors and other materials.Comment: 16 pages, 4 figures, accepted to Nature Material

Hierarchy of exchange interactions in the triangular-lattice spin-liquid YbMgGaO4_{4}

The spin-1/2 triangular lattice antiferromagnet YbMgGaO$_{4}$ has attracted recent attention as a quantum spin-liquid candidate with the possible presence of off-diagonal anisotropic exchange interactions induced by spin-orbit coupling. Whether a quantum spin-liquid is stabilized or not depends on the interplay of various exchange interactions with chemical disorder that is inherent to the layered structure of the compound. We combine time-domain terahertz spectroscopy and inelastic neutron scattering measurements in the field polarized state of YbMgGaO$_{4}$ to obtain better microscopic insights on its exchange interactions. Terahertz spectroscopy in this fashion functions as high-field electron spin resonance and probes the spin-wave excitations at the Brillouin zone center, ideally complementing neutron scattering. A global spin-wave fit to all our spectroscopic data at fields over 4T, informed by the analysis of the terahertz spectroscopy linewidths, yields stringent constraints on $g$-factors and exchange interactions. Our results paint YbMgGaO$_{4}$ as an easy-plane XXZ antiferromagnet with the combined and necessary presence of sub-leading next-nearest neighbor and weak anisotropic off-diagonal nearest-neighbor interactions. Moreover, the obtained $g$-factors are substantially different from previous reports. This works establishes the hierarchy of exchange interactions in YbMgGaO$_{4}$ from high-field data alone and thus strongly constrains possible mechanisms responsible for the observed spin-liquid phenomenology

Corporate Influence on Pakistani News Media: Journalists’ Perception

News making process is complex and there are several factors thatmay influence it. The power of corporate sector to influence mediapolicies and content is one of them. Journalists play pivotal role innews making process. The study, through survey aims toinvestigate the perceptions of the journalists for the possibleinfluence of corporate sector through advertising and publicrelations, on news media in Pakistan. A sample of 250 journalistswas selected randomly from major cities of Pakistan. Findings showthat journalists believe that corporations through advertising andpublic relations influence news media corporations both at a macroand micro level however, this influence is exerted on the journalistsnot directly but through the ownership policies

Politics for Environment: Youth Perception on Campaign for Billion Tree Tsunami to Combat Climate Change Situation in Pakistan

Pakistan is considered a highly vulnerable country because of the disastrous effects of climate change. Billion Tree Tsunami campaign by Pakistan Tehreek-e-Insaf (PTI) government in Khyber Pakhtunkhwa (KP) province of Pakistan in 2014 was the first attempt to mitigate climate change effects. The campaign was politicized and got media attention because of accusations of mismanagement, corruption and using the campaign for political motives by PTI. Studies on climate change communication assert that management of perception in such campaigns should be handled with great care as any is communication and misperception thus created could have serious consequences for the future of any effort carried out for climate change mitigation. Therefore, this study was conducted to know the perception of youth on the Billion Tree Tsunami campaign. Climate Change Risk Perception Model by Linden (2014) was used to develop a conceptual framework for the study. The quantitative method of the survey was used for data collection. Data was collected from five hundred respondents belonging to KP. It was found that the politicizing of billion tree tsunami campaign affected the perception of youth. The youth had a mixed perception of the campaign. They believe that they feel motivated to work for climate change mitigation after the campaign. It was found that the campaign was visible on media and PTI provided endorsing evidence from independent sources to support the campaign. On the other hand, there was a little effort for ensuring cross-sectional participation and minimizing opposition to it. It is also found that youth motivation to work for climate change mitigation is correlated to enhancing visibility and providing evidence through media whereas, it is not correlated to political affiliation

Conceptual data sampling for breast cancer histology image classification

Data analytics have become increasingly complicated as the amount of data has increased. One technique that is used to enable data analytics in large datasets is data sampling, in which a portion of the data is selected to preserve the data characteristics for use in data analytics. In this paper, we introduce a novel data sampling technique that is rooted in formal concept analysis theory. This technique is used to create samples reliant on the data distribution across a set of binary patterns. The proposed sampling technique is applied in classifying the regions of breast cancer histology images as malignant or benign. The performance of our method is compared to other classical sampling methods. The results indicate that our method is efficient and generates an illustrative sample of small size. It is also competing with other sampling methods in terms of sample size and sample quality represented in classification accuracy and F1 measure

Enhancement of solubility and release profile of simvastatin by co-crystallization with citric acid

Purpose: To enhance the solubility and dissolution profile of simvastatin (SIM) via co-crystallization with varying levels of citric acid using various techniques. Method: Simvastatin-citric acid (SIM-CA) co-crystals were prepared using dry grinding, slurry, liquidassisted grinding, and solvent evaporation techniques, and their various properties were compared. A total of twelve formulations (CC01 to CC12) were prepared. Optimized formulations were selected on the basis of dissolution profiles. Flow properties were evaluated using micromeritic analysis, yielding angle of repose, Carr’s index and Hausner’s ratio. Zeta sizer was employed to evaluate particle size distribution, while surface morphology was determined using scanning electron microscopy (SEM). Melting temperature, stability and physical interaction of simvastatin-citric acid co-crystals were determined by thermal analysis and FTIR. The crystalline nature of the co-crystals was evaluated by powder x-ray diffraction analysis, while solubility and dissolution studies were performed to determine in vitro drug release behavior. Results: Micromeritic analysis revealed good flow properties of SIM-CA co-crystals. Results of Zeta sizer analysis showed that the particle sizes of the co-crystals were in the nanometer range, while SEM revealed that the co-crystals had regular cubical shape. Thermal stability studies with TGA and DSC showed that the co-crystals were stable at temperatures exceeding 400 oC. FTIR results revealed minor shifts in 2956 and 1706 cm-1 peaks. Co-crystal formation was confirmed by PXRD data. The drug release profiles of the optimized formulations (CC02, CC07 and CC11) were 11.36 - 94.46, 12.36 - 95.46 and 13.36 - 96.46 %, respectively. There was significant improvement in solubilities of the optimum formulations, with values of 310.18, 427.21 and 522.02 % for CC02, CC07 and CC11, respectively. Conclusion: Citric acid improves the solubility and dissolution profile of the poorly water-soluble drug, simvastatin, which suggests that co-crystallization can potentially enhance the bioavailability of the drug

Companies Bankruptcy Prediction by Using Altman Models and Comparing Them

Bankruptcy prediction of economic institutions is considered a necessary matter at the present time in order to avoid the risks that may drive such institutions out of business. Given such fact, the current study was made to highlight the intellectual aspects of the subject of bankruptcy prediction and means of measuring it. There are five main types of models for predicting companies bankruptcy: one-way analysis of variance, multiple discriminant analysis, logarithmic analysis, recurrent algorithm analysis, and finally neural networks analysis, which is the most recent bankruptcy prediction method. These methods do not produce similar results. Most bankruptcy prediction studies used multiple discriminant analysis (MDA) and statistical methods for models development. These studies covered both large and small companies as well as private and public companies. MDA is the essence of this research paper which deals with Altman Model in detail and describes the changes that the original Z-Score equation has gone through. The study problem lies in arranging Altman Models for bankruptcy prediction of commercial companies in Iraq in accordance with the importance of each model