213 research outputs found
Study of dielectric relaxations in cellulose by combined DDS and TSC
In this work, thermally stimulated currents (TSC) analyses combined with dynamic dielectric spectroscopy (DDS) have been applied to the investigation of molecular mobility of cellulose. The correlation between results obtained by both methods allows us to attribute the low temperature DDS relaxation mode to the c-mode resolved in TSC. The values of its activation parameters point out that the chain mobility remains localized. At high temperature, the various dielectric relaxation phenomena are separated by applying a recent analytical protocol. The comparison between the activation enthalpy values obtained by DDS and TSC leads to the assignment of the socalled a-mode to cooperative movements of polymeric sequences. The Arrhenius behavior of a-relaxation time is explained using the strong/fragile pattern. The influence of water content on secondary and primary relaxation modes was examined as well
The ultimate tactics of self-referential systems
Mathematics is usually regarded as a kind of language. The essential behavior
of physical phenomena can be expressed by mathematical laws, providing
descriptions and predictions. In the present essay I argue that, although
mathematics can be seen, in a first approach, as a language, it goes beyond
this concept. I conjecture that mathematics presents two extreme features,
denoted here by {\sl irreducibility} and {\sl insaturation}, representing
delimiters for self-referentiality. These features are then related to physical
laws by realizing that nature is a self-referential system obeying bounds
similar to those respected by mathematics. Self-referential systems can only be
autonomous entities by a kind of metabolism that provides and sustains such an
autonomy. A rational mind, able of consciousness, is a manifestation of the
self-referentiality of the Universe. Hence mathematics is here proposed to go
beyond language by actually representing the most fundamental existence
condition for self-referentiality. This idea is synthesized in the form of a
principle, namely, that {\sl mathematics is the ultimate tactics of
self-referential systems to mimic themselves}. That is, well beyond an
effective language to express the physical world, mathematics uncovers a deep
manifestation of the autonomous nature of the Universe, wherein the human brain
is but an instance.Comment: 9 pages. This essay received the 4th. Prize in the 2015 FQXi essay
contest: "Trick or Truth: the Mysterious Connection Between Physics and
Mathematics
Memory interference effects in spin glasses
When a spin glass is cooled down, a memory of the cooling process is
imprinted in the spin structure. This memory can be disclosed in a continuous
heating measurement of the ac-susceptibility. E.g., if a continuous cooling
process is intermittently halted during a certain aging time at one or two
intermediate temperatures, the trace of the previous stop(s) is recovered when
the sample is continuously re-heated [1]. However, heating the sample above the
aging temperature, but keeping it below Tg, erases the memory of the thermal
history at lower temperatures. We also show that a memory imprinted at a higher
temperature can be erased by waiting a long enough time at a lower temperature.
Predictions from two complementary spin glass descriptions, a hierarchical
phase space model and a real space droplet picture are contested with these
memory phenomena and interference effects.
[1] K. Jonason, E. Vincent, J. Hammann, J. P. Bouchaud and P. Nordblad, Phys.
Rev. Lett. 31, 3243 (1998).Comment: 7 pages, 1 LaTex file + 5 figures in EPS Revised version of June 17,
1999 (minor changes), to appear in EPJ B around November 9
High-efficiency WSi superconducting nanowire single-photon detectors for quantum state engineering in the near infrared
We report on high-efficiency superconducting nanowire single-photon detectors
based on amorphous WSi and optimized at 1064 nm. At an operating temperature of
1.8 K, we demonstrated a 93% system detection efficiency at this wavelength
with a dark noise of a few counts per second. Combined with cavity-enhanced
spontaneous parametric down-conversion, this fiber-coupled detector enabled us
to generate narrowband single photons with a heralding efficiency greater than
90% and a high spectral brightness of
photons/(smWMHz). Beyond single-photon generation at large rate,
such high-efficiency detectors open the path to efficient multiple-photon
heralding and complex quantum state engineering
Computer identification of snoRNA genes using a Mammalian Orthologous Intron Database
Based on comparative genomics, we created a bioinformatic package for computer prediction of small nucleolar RNA (snoRNA) genes in mammalian introns. The core of our approach was the use of the Mammalian Orthologous Intron Database (MOID), which contains all known introns within the human, mouse and rat genomes. Introns from orthologous genes from these three species, that have the same position relative to the reading frame, are grouped in a special orthologous intron table. Our program SNO.pl searches for conserved snoRNA motifs within MOID and reports all cases when characteristic snoRNA-like structures are present in all three orthologous introns of human, mouse and rat sequences. Here we report an example of the SNO.pl usage for searching a particular pattern of conserved C/D-box snoRNA motifs (canonical C- and D-boxes and the 6 nt long terminal stem). In this computer analysis, we detected 57 triplets of snoRNA-like structures in three mammals. Among them were 15 triplets that represented known C/D-box snoRNA genes. Six triplets represented snoRNA genes that had only been partially characterized in the mouse genome. One case represented a novel snoRNA gene, and another three cases, putative snoRNAs. Our programs are publicly available and can be easily adapted and/or modified for searching any conserved motifs within mammalian introns
Differential regulation of non-protein coding RNAs from Prader-Willi Syndrome locus
Prader-Willi Syndrome (PWS) is a neurogenetic disorder caused by the deletion of imprinted genes on the paternally inherited human chromosome 15q11-q13. This locus harbours a long non-protein-coding RNA (U-UBE3A-ATS) that contains six intron-encoded snoRNAs, including the SNORD116 and SNORD115 repetitive clusters. The 3′-region of U-UBE3A-ATS is transcribed in the cis-antisense direction to the ubiquitin-protein ligase E3A (UBE3A) gene. Deletion of the SNORD116 region causes key characteristics of PWS. There are few indications that SNORD115 might regulate serotonin receptor (5HT2C) pre-mRNA processing. Here we performed quantitative real-time expression analyses of RNAs from the PWS locus across 20 human tissues and combined it with deep-sequencing data derived from Cap Analysis of Gene Expression (CAGE-seq) libraries. We found that the expression profiles of SNORD64, SNORD107, SNORD108 and SNORD116 are similar across analyzed tissues and correlate well with SNORD116 embedded U-UBE3A-ATS exons (IPW116). Notable differences in expressions between the aforementioned RNAs and SNORD115 together with the host IPW115 and UBE3A cis-antisense exons were observed. CAGE-seq analysis revealed the presence of potential transcriptional start sites originated from the U-UBE3A-ATS spanning region. Our findings indicate novel aspects for the expression regulation in the PWS locus
Experimental Rnomics: Towards The Identification And Characterization Of Non-Protein-Coding Ribonucleic Acids In Pathogenic Agent, Salmonella Typhi
RNA bukan-pengkod-protein (npcRNA) merupakan satu kelas pengawalatur-ribo
yang bertindak di dalam bentuk kompleks RNA-protein (sebagai RNPs) didalam
pelbagai laluan pengawalaturan. Tesis ini memberikan tumpuan ke atas_ pengenalpastian
npcRNA secara eksperimental daripada bakteria patogenik Salmonella enterica serovar
Typhi (S. Typhi), penyebab penyakit demam kepialu. Melalui pendekatan RNomiks
Eksperimental, 82 calon novel npcRNAdaripada perpustakaan cDNA S. Typhi telah
dikenalpasti dan dicirikan. Daripada jumlah ini, 28 telah ditranskrip daripada IGR, 29
ditranskrip di dalam arah antisense kepada ORF dan 18 dikenalpasti bertindihan dengan
ORF. Sementara 7 calon yang lain telah ditranskIlp daripada kawasan repititif dan
beberapa kedudukan bukan repitatif yang lain. Sebelas npcRNA merupakan npcRNAs
yang telahpun dilaporkan.
Non-protein-coding RNA (npcRNA) is a large class of riboregulators that act in
complex with proteins (as RNPs) in diverse regulatory pathways. This thesis focused on
the experimental identification of small npcRNAs from Salmonella enterica serovar
Typhi (s. Typhi), the aetiological agent of typhoid fever. By an Experimental RNomics
approach, 82 species of uncharacterized novel npcRNA candidates were identified from
library generated from different growth phases of a clinically isolated S. Typhi. From
this, 28 were transcribed from the IGRs, 29 were transcribed in the antisense orientation
of the ORFs and 18 were identified to overlap the ORFs. Another 7 candidates were
transcribed from repetitive regions and several non-repetitive locations. Eleven known
npcRNAs were also detected
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