904 research outputs found
Routing scheme for macro mobility handover in hierarchical mobile IPv6 network
Significant problems in basic mobile IPv6
occur due to its inability to support micro-mobility
because of long delay and high packet loss during
handover. Hierarchical mobile IPv6 (HMIPv6) as an
extension of basic Mobile IPv6 solves the problem by
separating the handover management to macromobility
and micro-mobility. HMIPv6 introduced a
new protocol element called Mobility Anchor Point
(MAP) to manage the mobility. HMIPv6 can reduce
the delay and the amount of signaling during
handover. However the protocol still cannot meet the
requirement for traffic that is delay sensitive such as
voice especially in macro mobility management.
Duplicate address detection and the transmission time
for the handover operation could cause high handover
delay
Optical delay control of large-spectral-bandwidth laser pulses
In this letter we report the first experimental observation of temporal delay
control of large-spectral-bandwidth multimode laser pulses by means of
electromagnetically induced transparency (EIT). We achieved controllable
retardation with limited temporal distortion of optical pulses with an input
spectral bandwidth of 3.3 GHz. The experimental results compare favorably with
theoretical predictions.Comment: Submitted to Optics Letters (January 2009
Pedagogical reflections of Muslim-Filipino Madrasah teachers: A phenomenological study
The purpose of the paper wasto explore the pedagogical reflections of Madrasah teachers or Asatidzas program implementers of Madrasah Education Program (MEP) in selected Arabic Language and Islamic Values Education (ALIVE) schools in Metro Manila, Philippines and identify salient themes on their lived experiences on teaching and learning process. Thisstudy utilized qualitative method of research usingtranscendental phenomenological approach of Moustakas (1994) as adapted from Husserl (1931), employing in-depth interviews and understanding of the participants’ description of their lived experiences. The authors used purposive sampling with ten research participants across Metro Manila. There were four (4) major themes identified in the study: (1) Teacher with divine responsibility; (2) Teacher as role model; (3) Teacher equipped with pedagogical practices; (4) Student-centered approach to teaching and learning. This study providedenrichment of evidence-based research especially on the lived experiences of grassroots implementers. Fewer studies on MEP were conducted especially on instructional process and particularly in teaching and learning process in the Philippines. The results servedas groundwork for more in-depth understanding of Madrasah teachers’ pedagogical practices as an integral part of the educative process
Optimal shapes of compact strings
Optimal geometrical arrangements, such as the stacking of atoms, are of
relevance in diverse disciplines. A classic problem is the determination of the
optimal arrangement of spheres in three dimensions in order to achieve the
highest packing fraction; only recently has it been proved that the answer for
infinite systems is a face-centred-cubic lattice. This simply stated problem
has had a profound impact in many areas, ranging from the crystallization and
melting of atomic systems, to optimal packing of objects and subdivision of
space. Here we study an analogous problem--that of determining the optimal
shapes of closely packed compact strings. This problem is a mathematical
idealization of situations commonly encountered in biology, chemistry and
physics, involving the optimal structure of folded polymeric chains. We find
that, in cases where boundary effects are not dominant, helices with a
particular pitch-radius ratio are selected. Interestingly, the same geometry is
observed in helices in naturally-occurring proteins.Comment: 8 pages, 3 composite ps figure
Stereochemical Criteria for Prediction of the Effects of Proline Mutations on Protein Stability
When incorporated into a polypeptide chain, proline (Pro) differs from all other naturally occurring amino acid residues in two important respects. The φ dihedral angle of Pro is constrained to values close to −65° and Pro lacks an amide hydrogen. Consequently, mutations which result in introduction of Pro can significantly affect protein stability. In the present work, we describe a procedure to accurately predict the effect of Pro introduction on protein thermodynamic stability. Seventy-seven of the 97 non-Pro amino acid residues in the model protein, CcdB, were individually mutated to Pro, and the in vivo activity of each mutant was characterized. A decision tree to classify the mutation as perturbing or nonperturbing was created by correlating stereochemical properties of mutants to activity data. The stereochemical properties including main chain dihedral angle φ and main chain amide H-bonds (hydrogen bonds) were determined from 3D models of the mutant proteins built using MODELLER. We assessed the performance of the decision tree on a large dataset of 163 single-site Pro mutations of T4 lysozyme, 74 nsSNPs, and 52 other Pro substitutions from the literature. The overall accuracy of this algorithm was found to be 81% in the case of CcdB, 77% in the case of lysozyme, 76% in the case of nsSNPs, and 71% in the case of other Pro substitution data. The accuracy of Pro scanning mutagenesis for secondary structure assignment was also assessed and found to be at best 69%. Our prediction procedure will be useful in annotating uncharacterized nsSNPs of disease-associated proteins and for protein engineering and design
Statics, metastable states and barriers in protein folding: A replica variational approach
Protein folding is analyzed using a replica variational formalism to
investigate some free energy landscape characteristics relevant for dynamics. A
random contact interaction model that satisfies the minimum frustration
principle is used to describe the coil-globule transition (characterized by
T_CG), glass transitions (by T_A and T_K) and folding transition (by T_F).
Trapping on the free energy landscape is characterized by two characteristic
temperatures, one dynamic, T_A the other static, T_K (T_A> T_K), which are
similar to those found in mean field theories of the Potts glass. 1)Above T_A,
the free energy landscape is monotonous and polymer is melted both dynamically
and statically. 2)Between T_A and T_K, the melted phase is still dominant
thermodynamically, but frozen metastable states, exponentially large in number,
appear. 3)A few lowest minima become thermodynamically dominant below T_K,
where the polymer is totally frozen. In the temperature range between T_A and
T_K, barriers between metastable states are shown to grow with decreasing
temperature suggesting super-Arrhenius behavior in a sufficiently large system.
Due to evolutionary constraints on fast folding, the folding temperature T_F is
expected to be higher than T_K, but may or may not be higher than T_A. Diverse
scenarios of the folding kinetics are discussed based on phase diagrams that
take into account the dynamical transition, as well as the static ones.Comment: 41 pages, LaTeX, 9 EPS figure
Dinamica unor indici biochimici în tratamentul litiazei urinare cu Shilintong
Summary
Urinary enzymes N-acetil-β-D-glucosam inidase (NAG), Lactate dehydrogenase (LDH), β2-microglobulin (β2-M) levels in blood and urine were measured in the 20 patients with urolithiasis treated with Shilintong and in 26 patients treated using alternate drugs for urolithiasis in association with antibacterial treatment. It was found that the levels of β2-M were high in both the groups before the treatment in com parision to the control group. While it was found that after the treatment the high level of β2-M are present only in first group, this indicates the process of tubular damage. The levels of NAG and LDH were found to remain high in both the groups
before and after the treatment this indicates cellular dam age to the tubules indicating the development of
pyelonephrites. Shellintong has been found not to be nephrotoxic
Protein folding using contact maps
We present the development of the idea to use dynamics in the space of
contact maps as a computational approach to the protein folding problem. We
first introduce two important technical ingredients, the reconstruction of a
three dimensional conformation from a contact map and the Monte Carlo dynamics
in contact map space. We then discuss two approximations to the free energy of
the contact maps and a method to derive energy parameters based on perceptron
learning. Finally we present results, first for predictions based on threading
and then for energy minimization of crambin and of a set of 6 immunoglobulins.
The main result is that we proved that the two simple approximations we studied
for the free energy are not suitable for protein folding. Perspectives are
discussed in the last section.Comment: 29 pages, 10 figure
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