Lack Of Structural Constraints Research Articles

A quantitative evaluation of online translators using Hindi web queries

Understanding machine translation (MT) quality is becoming more and more important as MT usage continues to rise in the translation industry. The acceptance of MT output based on their performance and, ultimately, how acceptable the translators actually are, have received relatively less attention so far. MT plays a vital role in CLIR systems and their retrieval efficiency is directly proportional to the translation accuracy of the queries. The varied meanings of words, sentences carrying multiple interpretations, and differing grammatical structures across languages contribute to the complexity of the MT task. The lack of structural constraints and the presence of ambiguity further compound the complications especially in case of web queries. The objective of this work is to assess the accuracy of free online translators in translating Hindi web queries. The accuracy of the translators has been evaluated on various metrics, i.e., BLEU, NIST, METEOR, hLepor, CHRF and GLEU. Our findings indicate that the translation accuracy for longer queries is higher than the shorter ones. Overall Google translator’s performance has been found the best while Systran performs the worst with 42.06% performance difference between the two. The present work intends to help researchers in further evaluating and analyzing the MT systems specially in context of web query translation, ultimately leading to improved translation quality and retrieval accuracy in CLIR.

Evolution of a giant intromittent organ in Scydmaeninae (Coleoptera: Staphylinidae): Functional morphology of the male postabdomen in Mastigini

We compared the postabdominal architecture of Mastigini with extremely long (Stenomastigus) or short (Palaeostigus) aedeagus. A novel mode of copulation was discovered: males of Stenomastigus insert a paramere between the female's abdomen and elytra, and the intromission is stabilized by several structures of both sexes. The intrinsic aedeagal mechanism is indicated as responsible for inflating the endophallus, and the long flagellum does not penetrate the ductus spermathecae during copulation. The structure of the flagellum suggests that it is primarily responsible for the sperm transfer. Asymmetrical postabdominal rotators of the aedeagus were only found in Stenomastigus; they presumably facilitate the withdrawal of the genitalia; their origin as bundles separated from larger muscles is postulated. We discuss a scenario in which the evolution of elongated genitalia was facilitated by the lack of structural constraints and existing preadaptations. Benefits of stabilizing the copulation and intromission are indicated as the driving force for the evolution of extremely long aedeagi, while the short aedeagi might have the advantage of freedom of movements facilitating the initiation of copulation by males. Disruptive selection is suggested as a working hypothesis to further investigate mechanisms that have played a role in the evolution of genital structures of Mastigini.

Handcuffing the hegemon: The paradox of state power under unipolarity

The exercise of state power in global politics often involves a vexing paradox: strategies intended to create or project power may end up reducing it. Under unipolarity, the lack of structural constraints in the international system do as much to undermine hegemonic power as to magnify it. Through an examination of the structure and process of unipolar politics, the three works reviewed in this article investigate the unintended consequences of preponderant power, especially as it relates to American grand strategy. As such, the paradox of state power has direct implications for the durability and relative peacefulness of the unipolar politics.

A kinetic approach to distinguish between catalytic mechanisms of protein kinase autophosphorylation

Protein kinase autoactivation, via phosphorylation of the activation loop, is a common regulatory mechanism in phosphorylation‐dependent signaling cascades. Their molecular mechanisms can be simply categorized to intra‐molecular(in cis) or inter‐molecular(in trans). Specifically, the trans‐autophosphorylation kinases vary in their initiation modes. In this study, we give a full analysis for the four initiation modes in trans‐autophosphorylation and develop a kinetic approach, which is based on the kinetic theory of substrate reaction during modification of enzyme activity, to quantitively distinguish them. Applying our kinetic method to p21‐activated kinase 2 kinase domain(PAK2‐KD), we identified the molecular mechanism of PAK2‐KD trans‐autophosphorylation and determined all microscopic kinetic constants for its autoactivation process, coincident with our structural studies on PAK1 kinase domain. The unphosphorylated PAK2‐KD, which is lack of structural constraints in context, could dynamically adopt both the active and inactive conformations, thus initiates the autoactivation process differently from the full‐length PAK2. Our kinetic method gives a general solution to describe distinct catalytic mechanisms of protein kinase autophosphorylation and is particular useful during the fast modification reaction.

The structure of the ankyrin-binding site of β-spectrin reveals how tandem spectrin-repeats generate unique ligand-binding properties

Spectrin and ankyrin participate in membrane organization, stability, signal transduction, and protein targeting; their interaction is critical for erythrocyte stability. Repeats 14 and 15 of betaI-spectrin are crucial for ankyrin recognition, yet the way spectrin binds ankyrin while preserving its repeat structure is unknown. We have solved the crystal structure of the betaI-spectrin 14,15 di-repeat unit to 2.1 A resolution and found 14 residues critical for ankyrin binding that map to the end of the helix C of repeat 14, the linker region, and the B-C loop of repeat 15. The tilt (64 degrees) across the 14,15 linker is greater than in any published di-repeat structure, suggesting that the relative positioning of the two repeats is important for ankyrin binding. We propose that a lack of structural constraints on linker and inter-helix loops allows proteins containing spectrin-like di-repeats to evolve diverse but specific ligand-recognition sites without compromising the structure of the repeat unit. The linker regions between repeats are thus critical determinants of both spectrin's flexibility and polyfunctionality. The putative coupling of flexibility and ligand binding suggests a mechanism by which spectrin might participate in mechanosensory regulation.