5,649 research outputs found
Annealing study of A1/GaSb contact with the use of doppler broadening technique
Using a monoenergetic positron beam, annealing study of the Al/n-GaSb system was performed by monitoring the Doppler broadening of the annihilation radiation as a function of the positron implanting energy. The S-parameter against positron energy data was successfully fitted by a three-layer model (Al/interface/GaSb). The annealing out of the open volume defects in the polycrystalline Al layer was revealed by the decrease in the S-parameter and the increase in the effective diffusion length of the Al layer. For the as-deposited samples, aβΌ5 nm interfacial region with S-parameter larger than those of the Al overlayer and the bulk was identified. After the 400^ΒΊC annealing, this interfacial region extends to over 40 nm and its S-parameter dramatically drops. This is possibly due to the new phase formation at the interface. Annealing behaviors of SB and L+,B of the GaSb bulk showed the annealing out of positron traps (possibly the VGa-related defect) at 250ΒΊC. However, a further annealing at 400ΒΊC induces the formation of positron traps, which are possibly of another kind of VGa-related defect and the positron shallow trap GaSb antisite.published_or_final_versionProceedings of the 35th Polish Seminar on Positron Annihilation (PSPA), Turawa, Poland, 20-24 September 2004. In Acta Physica Polonica Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics, 2005, v. 107 n. 5, p. 874-87
Increased regulatory T-cell numbers distinguish high-risk breast cancer patients and those at risk of late relapse
Ionic liquids for energy, materials, and medicine.
As highlighted by the recent ChemComm web themed issue on ionic liquids, this field continues to develop beyond the concept of interesting new solvents for application in the greening of the chemical industry. Here some current research trends in the field will be discussed which show that ionic liquids research is still aimed squarely at solving major societal issues by taking advantage of new fundamental understanding of the nature of these salts in their low temperature liquid state. This article discusses current research trends in applications of ionic liquids to energy, materials, and medicines to provide some insight into the directions, motivations, challenges, and successes being achieved with ionic liquids today
Reflections on Tiles (in Self-Assembly)
We define the Reflexive Tile Assembly Model (RTAM), which is obtained from
the abstract Tile Assembly Model (aTAM) by allowing tiles to reflect across
their horizontal and/or vertical axes. We show that the class of directed
temperature-1 RTAM systems is not computationally universal, which is
conjectured but unproven for the aTAM, and like the aTAM, the RTAM is
computationally universal at temperature 2. We then show that at temperature 1,
when starting from a single tile seed, the RTAM is capable of assembling n x n
squares for n odd using only n tile types, but incapable of assembling n x n
squares for n even. Moreover, we show that n is a lower bound on the number of
tile types needed to assemble n x n squares for n odd in the temperature-1
RTAM. The conjectured lower bound for temperature-1 aTAM systems is 2n-1.
Finally, we give preliminary results toward the classification of which finite
connected shapes in Z^2 can be assembled (strictly or weakly) by a singly
seeded (i.e. seed of size 1) RTAM system, including a complete classification
of which finite connected shapes be strictly assembled by a "mismatch-free"
singly seeded RTAM system.Comment: New results which classify the types of shapes which can
self-assemble in the RTAM have been adde
Π£Π²Π΅Π»ΠΈΡΠ΅Π½ΠΈΠ΅ ΡΠ΅ΠΌΠΏΠΎΠ² ΠΏΡΠΈΡΠΎΡΡΠ° Π·Π°ΠΏΠ°ΡΠΎΠ² ΡΠ³Π»Π΅Π²ΠΎΠ΄ΠΎΡΠΎΠ΄ΠΎΠ² Ρ ΠΏΠΎΠΌΠΎΡΡΡ ΠΈΠ½Π½ΠΎΠ²Π°ΡΠΈΠΎΠ½Π½ΡΡ ΡΠ΅Ρ Π½ΠΎΠ»ΠΎΠ³ΠΈΠΉ Π½Π° ΠΏΡΠΈΠΌΠ΅ΡΠ΅ ΠΠΌΡΠΊΠΎΠΉ ΠΎΠ±Π»Π°ΡΡΠΈ
ΠΡΠΎΠ²Π΅Π΄Π΅Π½ Π°Π½Π°Π»ΠΈΠ· ΠΏΠ΅ΡΡΠΏΠ΅ΠΊΡΠΈΠ² Π½Π΅ΡΡΠ΅Π³Π°Π·ΠΎΠ½ΠΎΡΠ½ΠΎΡΡΠΈ ΠΠΌΡΠΊΠΎΠΉ ΠΎΠ±Π»Π°ΡΡΠΈ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ Π΄Π°Π½Π½ΡΡ
ΠΈΠ½Π½ΠΎΠ²Π°ΡΠΈΠΎΠ½Π½ΠΎΠΉ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠΈ ΠΊΠ²Π°Π½ΡΠΎΠ²ΠΎ-ΠΎΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠΈΠ»ΡΡΡΠ°ΡΠΈΠΈ ΠΊΠΎΡΠΌΠΎΡΠ½ΠΈΠΌΠΊΠΎΠ². ΠΡΠΈΠ²Π΅Π΄Π΅Π½Ρ ΡΠΈΠ·ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΏΡΠΈΠ½ΡΠΈΠΏΡ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠΈ ΠΊΠ²Π°Π½ΡΠΎΠ²ΠΎ-ΠΎΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠΈΠ»ΡΡΡΠ°ΡΠΈΠΈ. ΠΠ° ΠΏΡΠΈΠΌΠ΅ΡΠ΅ ΠΠΌΡΠΊΠΎΠΉ ΠΎΠ±Π»Π°ΡΡΠΈ ΠΏΠΎΠΊΠ°Π·Π°Π½Π° ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠΈ ΠΊΠ²Π°Π½ΡΠΎΠ²ΠΎ-ΠΎΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠΈΠ»ΡΡΡΠ°ΡΠΈΠΈ ΠΏΡΠΈ ΡΠ΅ΡΠ΅Π½ΠΈΠΈ Π·Π°Π΄Π°ΡΠΈ ΠΏΠΎΠ²ΡΡΠ΅Π½ΠΈΡ ΡΠ΅ΠΌΠΏΠΎΠ² ΠΏΡΠΈΡΠΎΡΡΠ° Π·Π°ΠΏΠ°ΡΠΎΠ² ΡΠ³Π»Π΅Π²ΠΎΠ΄ΠΎΡΠΎΠ΄Π½ΠΎΠ³ΠΎ ΡΡΡΡΡ
Sequence learning in Associative Neuronal-Astrocytic Network
The neuronal paradigm of studying the brain has left us with limitations in
both our understanding of how neurons process information to achieve biological
intelligence and how such knowledge may be translated into artificial
intelligence and its most brain-derived branch, neuromorphic computing.
Overturning our fundamental assumptions of how the brain works, the recent
exploration of astrocytes is revealing that these long-neglected brain cells
dynamically regulate learning by interacting with neuronal activity at the
synaptic level. Following recent experimental evidence, we designed an
associative, Hopfield-type, neuronal-astrocytic network and analyzed the
dynamics of the interaction between neurons and astrocytes. We show that
astrocytes were sufficient to trigger transitions between learned memories in
the neuronal component of the network. Further, we mathematically derived the
timing of the transitions that was governed by the dynamics of the
calcium-dependent slow-currents in the astrocytic processes. Overall, we
provide a brain-morphic mechanism for sequence learning that is inspired by,
and aligns with, recent experimental findings. To evaluate our model, we
emulated astrocytic atrophy and showed that memory recall becomes significantly
impaired after a critical point of affected astrocytes was reached. This
brain-inspired and brain-validated approach supports our ongoing efforts to
incorporate non-neuronal computing elements in neuromorphic information
processing.Comment: 8 pages, 5 figure
Stable ultrahigh-density magneto-optical recordings using introduced linear defects
The stability of data bits in magnetic recording media at ultrahigh densities
is compromised by thermal `flips' -- magnetic spin reversals -- of nano-sized
spin domains, which erase the stored information. Media that are magnetized
perpendicular to the plane of the film, such as ultrathin cobalt films or
multilayered structures, are more stable against thermal self-erasure than
conventional memory devices. In this context, magneto-optical memories seem
particularly promising for ultrahigh-density recording on portable disks, and
bit densities of 100 Gbit inch have been demonstrated using recent
advances in the bit writing and reading techniques. But the roughness and
mobility of the magnetic domain walls prevents closer packing of the magnetic
bits, and therefore presents a challenge to reaching even higher bit densities.
Here we report that the strain imposed by a linear defect in a magnetic thin
film can smooth rough domain walls over regions hundreds of micrometers in
size, and halt their motion. A scaling analysis of this process, based on the
generic physics of disorder-controlled elastic lines, points to a simple way by
which magnetic media might be prepared that can store data at densities in
excess of 1 Tbit inch.Comment: 5 pages, 4 figures, see also an article in TRN News at
http://www.trnmag.com/Stories/041801/Defects_boost_disc_capacity_041801.htm
Treatment of primary autoimmune cerebellar ataxia with mycophenolate
Immune-mediated ataxias account for a substantial number of sporadic otherwise idiopathic ataxias. Despite some well-characterised entities such as paraneoplastic cerebellar degeneration where diagnostic markers exist, the majority of immune ataxias remained undiagnosed and untreated. We present here our experience in the treatment of suspected primary autoimmune cerebellar ataxia (PACA) using mycophenolate. All patients reported attend the Sheffield Ataxia Centre on a regular basis and had undergone extensive investigations, including genetic testing using next-generation sequencing, with other causes of ataxia excluded. The diagnosis of PACA was strongly suspected based on investigations, pattern of disease progression, and cerebellar involvement. Patients were treated with mycophenolate and monitored using MR spectroscopy of the cerebellar vermis. Thirty patients with PACA are reported here. Of these, 22 received mycophenolate (group 1). The remaining 8 were not on treatment (group 2-control group). Out of the 22 treated patients, 4 underwent serial MR spectroscopy prior to starting treatment and thus were used as controls making the total number of patients in the control group 12. The mean change of the MRS within the vermis (NAA/Cr area ratio) in the treatment group was +β0.144βΒ±β0.09 (improved) and in the untreated group ββ0.155βΒ±β0.06 (deteriorated). The difference was significant. We also demonstrated a strong correlation between the spectroscopy and the SARA score. We have demonstrated the effectiveness of mycophenolate in the treatment of PACA. The results suggest that immune-mediated ataxias are potentially treatable, and that there is a need for early diagnosis to prevent permanent neurological deficit. The recently published diagnostic criteria for PACA would hopefully aid the diagnosis and treatment of this entity
Mining Diversity on Social Media Networks
The fast development of multimedia technology and increasing availability of network bandwidth has given rise to an abundance of network data as a result of all the ever-booming social media and social websites in recent years, e.g., Flickr, Youtube, MySpace, Facebook, etc. Social network analysis has therefore become a critical problem attracting enthusiasm from both academia and industry. However, an important measure that captures a participantβs diversity in the network has been largely neglected in previous studies. Namely, diversity characterizes how diverse a given node connects with its peers. In this paper, we give a comprehensive study of this concept. We first lay out two criteria that capture the semantic meaning of diversity, and then propose a compliant definition which is simple enough to embed the idea. Based on the approach, we can measure not only a userβs sociality and interest diversity but also a social mediaβs user diversity. An efficient top-k diversity ranking algorithm is developed for computation on dynamic networks. Experiments on both synthetic and real social media datasets give interesting results, where individual nodes identified with high diversities are intuitive
Nodal quasiparticle meltdown in ultra-high resolution pump-probe angle-resolved photoemission
High- cuprate superconductors are characterized by a strong
momentum-dependent anisotropy between the low energy excitations along the
Brillouin zone diagonal (nodal direction) and those along the Brillouin zone
face (antinodal direction). Most obvious is the d-wave superconducting gap,
with the largest magnitude found in the antinodal direction and no gap in the
nodal direction. Additionally, while antinodal quasiparticle excitations appear
only below , superconductivity is thought to be indifferent to nodal
excitations as they are regarded robust and insensitive to . Here we
reveal an unexpected tie between nodal quasiparticles and superconductivity
using high resolution time- and angle-resolved photoemission on optimally doped
BiSrCaCuO. We observe a suppression of the nodal
quasiparticle spectral weight following pump laser excitation and measure its
recovery dynamics. This suppression is dramatically enhanced in the
superconducting state. These results reduce the nodal-antinodal dichotomy and
challenge the conventional view of nodal excitation neutrality in
superconductivity.Comment: 7 pages, 3 figure. To be published in Nature Physic
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