共查询到20条相似文献,搜索用时 31 毫秒
1.
Beatriz Pérez-Artacho Visitación Gallardo M. Adolfina Ruiz José L. Arias 《Journal of nanoparticle research》2012,14(4):768
A reproducible methodology is described for the synthesis, by following the double emulsion/solvent evaporation technique,
of magnetic nanocomposites (average diameter ≈ 135 nm) consisting of maghemite nuclei and a biodegradable poly(d,l-lactide-co-glycolide) matrix. The heterogeneous structure of the nanoparticles can confer them the responsiveness to magnetic gradients,
giving both the possibility of their use as a drug delivery system and adequate heating characteristics for a hyperthermia
effect. The physical chemistry of the nanocomposites was extensively characterized, this establishing that their surface properties
were similar to that of pure poly(d,l-lactide-co-glycolide). From an electrokinetic point of view, zeta potential determinations (as a function of the ionic strength, and
pH) pointed out that the nanocomposites were almost indistinguishable from the copolymer. The surface thermodynamic analysis
agreed with the electrophoretic one in suggesting that the coverage of the magnetic nuclei was complete, since the hydrophilic
nature of maghemite was modified and the nanoparticles turned into hydrophobic, just like the copolymer, when they were embedded
into poly(d,l-lactide-co-glycolide). The magnetic behaviours of the composite nanoparticles were also checked. Their heating properties were studied
in vitro in a high-frequency alternating gradient of magnetic field: a stable maximum temperature of 47 °C was satisfactorily
achieved within 45 min. Blood compatibility of the nanocomposites was also defined in vitro. To our knowledge, this is the
first time that such kind of magnetic-sensitive nanoformulation with very promising characteristics (e.g. blood compatibility,
magnetic drug targeting capabilities, and hyperthermia) has been developed for therapeutic purposes. 相似文献
2.
Naresh Dadhich Josep M. Pons Kartik Prabhu 《General Relativity and Gravitation》2012,44(10):2595-2601
The necessary and sufficient condition for the thermodynamical universality of the static spherically symmetric Lovelock black hole is that it is the Nth order pure Lovelock Λ-vacuum solution. By universality we mean the thermodynamical parameters: temperature and entropy always bear the same relation to the horizon radius for d = 2N + 1, 2N + 2 dimensions for all N which is the degree of the Lovelock polynomial. For instance, the entropy always goes in terms of the horizon radius as r h and r h 2, respectively for the odd and even dimensions. Not only that the universality uniquely identifies the pure Lovelock black hole with Λ, it is the characterizing property of this class of black holes. 相似文献
3.
Krishna Pal Singh Saurabh Ahalawat Ramesh Kumar Prajapati Satish Kumar Prashant Singh Dhawan Sandeef Kumar 《Ionics》2010,16(6):529-537
Molecularly imprinted polymer (MIP) membranes were used to develop highly sensitive chemical sensors for the detection of
herbicide 2,4-dichlorophenoxy acetic acid (2,4-d). The 2,4-d imprinted composite MIP membranes were prepared, and the characterization was done by UV-VIS spectrophotometer, Fourier transform
infrared spectroscopy, and scanning electron microscopy, and the same were fitted in a new electrochemical sensor model. Membrane
electroconductivity measurements were performed by applying a small-amplitude alternating voltage (20 mV) with a varying frequency
from 20 Hz to 80 kHz generated by a low-frequency wave form generator. The measured changes in the membrane ionic/electric
conductivity as a function of 2,4-d concentration was allowed to evaluate the recognition properties of the prepared membrane. This sensor is useful in detecting
2,4-d herbicide having concentration range 10-3 M to 10-6 M. The cross-selectivity of the sensor, reproducibility of results, and reusability of MIP membrane were examined and found
remarkable and recommendable. 相似文献
4.
We show that the classical Nambu-Goto string inD dimensions admits Poincaré invariance ind dimensions (d⩽D) if (i)d − 2 of the transverse co-ordinatesx
i are periodic and the rest quasi-periodic involving a real orthogonal matrix with (D − d) (D − d − 1)/2 free parameters, or if (ii)d − 2 ofx
i obey Neumann and the rest obey a boundary condition involvingN free parameters, whereN=(D − d)2/2 ifD − d is even, andN=[(D − d)2 − 1]/2 ifD − d is odd. 相似文献
5.
P. E. Kornilovitch R. N. Bicknell J. S. Yeo 《Applied Physics A: Materials Science & Processing》2009,95(4):999-1004
Fully-connected mesh networks with local connections are described. Each connector links only nearest neighbors of the node lattice and carries enough passive pass-through
vias to provide direct one-to-one links between all the nodes. If the nodes form a one-dimensional ring, then each connector
must contain at least N(N−1)/2 physical channels. However, if the nodes are arranged in a d-dimensional hyper-torus, the number of channels per connector drops to N(N
1/d
−1)/2, which scales much more favorably at large N. Such arrangements can provide fully-meshed connectivity when parts of the network are physically inaccessible or when the
network needs to be scaled up in a modular fashion. 相似文献
6.
J. Z. Xin K. L. Jim J. Yang X. J. Gong L. Q. Chen F. Gao Y. H. Tsang H. L. W. Chan C. W. Leung 《Applied Physics A: Materials Science & Processing》2012,107(1):109-115
A one-dimensional photonic crystal working in the terahertz (THz) range was designed and implemented. To facilitate the design,
the transmission properties of strontium titanate crystals were characterized by THz-time-domain spectroscopy. Relatively
high refractive index (∼18.5) and transmission ratio (0.08) were observed between 0.2 to 1 THz. A stacked structure of (Si
d
Si/STO d
STO)
N
/Si d
Si was then designed, with transmission spectra calculated by the transfer matrix method. The effects of the filling ratio (d
STO/(d
Si+d
STO)), periodicity (d
Si+d
STO) and the number of repeats N on the transmission of PC were investigated. The effect of introducing a defect layer was also studied. Based on these, Si/STO
multilayers with STO defect thickness of 125 μm and 200 μm were measured. The shift of the defect mode was observed and compared
with the calculations. 相似文献
7.
Y Hariharan M P Janawadkar T S Radhakrishnan A L E Terrance G A Dixit V S Raghunathan 《Pramana》1986,26(6):513-524
Titanium-rich transition metal alloys are metastable in their quenched boc β phase. The instability is relieved by low temperature
structural transformations. We have investigated this in a series of Ti-Nb alloys, through the measurements of electrical
resistivity (ρ), superconducting transition temperature and upper critical field. Supporting structural evidence has been
obtained from transmission electron microscopy (tem) and x-ray studies. It is shown that both ρ and dρ/dT can be used as useful indices of this instability. The enhanced value of resistivity on account of the instability results
in the enhancement of upper critical field as shown from dH
c2/dT measurements. 相似文献
8.
Domingos H. U. Marchetti William R. P. Conti Leonardo F. Guidi 《Journal of statistical physics》2008,132(5):811-838
A continuous version of the hierarchical spherical model at dimension d=4 is investigated. Two limit distributions of the block spin variable X
γ
, normalized with exponents γ=d+2 and γ=d at and above the critical temperature, are established. These results are proven by solving certain evolution equations corresponding
to the renormalization group (RG) transformation of the O(N) hierarchical spin model of block size L
d
in the limit L
↓1 and N→∞. Starting far away from the stationary Gaussian fixed point the trajectories of these dynamical system pass through two
different regimes with distinguishable crossover behavior. An interpretation of this trajectories is given by the geometric
theory of functions which describe precisely the motion of the Lee–Yang zeroes. The large-N limit of RG transformation with L
d
fixed equal to 2, at the criticality, has recently been investigated in both weak and strong (coupling) regimes by Watanabe
(J. Stat. Phys. 115:1669–1713, 2004) . Although our analysis deals only with N=∞ case, it complements various aspects of that work.
D.H.U. Marchetti partially supported by CNPq and FAPESP.
W.R.P. Conti supported by FAPESP under grant 05/57416-8. 相似文献
9.
Neeraj Dwivedi Sushil Kumar C. M. S. Rauthan O. S. Panwar 《Applied Physics A: Materials Science & Processing》2011,102(1):225-230
Nanoindentation testing was performed on nitrogen (N2) incorporated diamond-like carbon (N-DLC) films and deposited using radio-frequency plasma-enhanced chemical vapor deposition
technique, with varied percentage of nitrogen partial pressures of 0, 44.4, 66.6, and 76.1%. The values of nanohardness (H) and elastic modulus (E) of these films were obtained from 38 to 22 GPa and 462 to 330 GPa, respectively, as the partial pressure of N2 increases from 0 to 76.1%. Further, these films were studied for % elastic recovery, ratio between residual displacement
after load removal and displacement at maximum load (d
res/d
max ), plastic deformation energy and plasticity index parameter (H/E). Both hardness per unit stress and plasticity index per unit stress were found to be maximum at N2 partial pressure of 76.1%. X-ray photoelectron spectroscopy measurements confirmed the presence of N2 in these films. 相似文献
10.
Saulius Mickevičius Darius Germanas Ramutis K. Kalinauskas 《Central European Journal of Physics》2012,10(2):421-428
We present a new independent scheme of SO(3) group transformations suitable for the N particle system, composed of N − 1 and 1 particle subsystems, where N − 1 particles have their own intrinsic clusterization. The simple expressions for corresponding four-particle harmonic-oscillator
transformation brackets are presented, as well as their simplifications for the special values of mass ratio parameters d = 0, d → ∞ and d
1 = 0, d
1 → ∞. 相似文献
11.
Williams AA Fakayode SO Alptürk O Jones CM Lowry M Strongin RM Warner IM 《Journal of fluorescence》2008,18(2):285-296
Novel fluorescent chiral molecular micelles (FCMMs) were synthesized, characterized, and employed as chiral selectors for
enantiomeric recognition of non-fluorescent chiral molecules using steady state fluorescence spectroscopy. The sensitivity
of the fluorescence technique allowed for investigation of low concentrations of chiral selector (3.0 × 10−5 M) and analyte (5.0 × 10−6 M) to be used in these studies. The chiral interactions of glucose, tartaric acid, and serine in the presence of FCMMs poly(sodium
N-undecanoyl-l-tryptophanate) [poly-l-SUW], poly(sodium N-undecanoyl-l-tyrosinate) [poly-l-SUY], and poly(sodium N-undecanoyl-l-phenylalininate) [poly-SUF] were based on diastereomeric complex formation. Poly-l-SUW had a significant fluorescence emission spectral difference as compared to poly-l-SUY and poly-l-SUF for the enantiomeric recognition of glucose, tartaric acid, and serine. Studies with the hydrophobic molecule α-pinene
suggested that poly-l-SUY and poly-l-SUF had better chiral discrimination ability for hydrophobic analytes as compared to hydrophilic analytes. Partial-least-squares
regression modeling (PLS-1) was used to correlate changes in the fluorescence emission spectra of poly-l-SUW due to varying enantiomeric compositions of glucose, tartaric acid, and serine for a set of calibration samples. Validation
of the calibration regression models was determined by use of a set of independently prepared samples of the same concentration
of chiral selector and analyte with varying enantiomeric composition. Prediction ability was evaluated by use of the root-mean-square
percent relative error (RMS%RE) and was found to range from 2.04 to 4.06%.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
C?t?lin I. Carstea 《Communications in Mathematical Physics》2010,300(2):487-528
The existence of co-rotational finite time blow up solutions to the wave map problem from ${\mathbb{R}^{2+1} \to N}The existence of co-rotational finite time blow up solutions to the wave map problem from
\mathbbR2+1 ? N{\mathbb{R}^{2+1} \to N} , where N is a surface of revolution with metric d
ρ
2 + g(ρ)2
dθ2, g an entire function, is proven. These are of the form u(t,r)=Q(l(t)t)+R(t,r){u(t,r)=Q(\lambda(t)t)+\mathcal{R}(t,r)} , where Q is a time independent solution of the co-rotational wave map equation −u
tt
+ u
rr
+ r
−1
u
r
= r
−2
g(u)g′(u), λ(t) = t
−1-ν, ν > 1/2 is arbitrary, and R{\mathcal{R}} is a term whose local energy goes to zero as t → 0. 相似文献
13.
Since violacein—an antibiotic, antiviral, and antiparasitic compound—exhibits poor solubility in water, polymeric poly-(d,l-lactide-co-glycolide) nanoparticles containing this compound improved its solubility and biological activity. The nanoparticles
were prepared by the nanoprecipitation method and characterized in terms of average diameter, zeta potential, drug loading,
polymer recovery, in vitro release kinetic, and in vitro antibacterial activity. Nanoparticles with diameters between 116
and 139 nm and negative-charged outer surfaces were obtained. Drug-loading efficiency and polymer recovery were 87 and 93%,
respectively. In vitro release kinetics assays showed that violacein loaded in these nanoparticles has sustained release behavior
until 5 days. Both free and nanoparticles-loaded violacein exhibited in vitro antibacterial activity against Staphylococcus aureus ATCC 29213 and ATCC 25923 strains and exhibiting around two to five times lower minimum inhibitory concentration (MIC) than
free violacein, respectively. The encapsulated violacein was efficient against methicilin-resistant Staphylococcus aureus (MRSA) strains. No significant activity against Escherichia coli and Salmonella enterica was found. 相似文献
14.
Hironobu Sakagawa 《Journal of statistical physics》2006,124(5):1255-1274
The main aim of this paper is to discuss the entropic repulsion of random interfaces between two hard walls. We consider the d (≥ 3)-dimensional Gaussian lattice field on ℝλ
N
, λ
N
= [−N, N]
d
∩ ℤ
d
and identify the repulsion of the field as N → ∞ under the condition that the field lies between two hard walls at the height level 0 and L in Λ
N
where L is large enough but finite. We also study the same problem for two layered interfaces case. 相似文献
15.
The statistics of energy levels for a disordered conductor are considered in the critical energy window near the mobility
edge. It is shown that, if the critical wave functions are multifractal, the one-dimensional gas of levels on the energy axis
is compressible, in the sense that the variance of the level number in an interval is 〈 (δN)2〉∼χ〈N〉 for 〈N〉≫1. The compressibility, χ=η/2d, is given exactly in terms of the multifractal exponent η =d−D
2 at the mobility edge in a d-dimensional system.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 355–360 (10 September 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
16.
N.V. Shevchenko V.B. Belyaev S.A. Rakityansky S.A. Sofianos W. Sandhas 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):143-146
Elastic ηd-scattering is considered within the Alt-Grassberger-Sandhas (AGS) formalism for various ηN input data. A three-body resonant state is found close to the ηd threshold. This resonance is sustained for different choices of the two-body ηN-scattering length a
ηN. The position of the resonance moves towards the ηd threshold when Rea
ηN is increased, and turns into a quasi-bound state at Rea
ηN∼ 0.7-0.8 fm depending on the choice of Ima
ηN.
Received: 12 June 2000 / Accepted: 3 August 2000 相似文献
17.
We calculate the process np → ηd near threshold using a separable potential model of the coupled ηN - πN - ππN subystems, and a relativistic three-body calculation for the ηd scattering amplitude. The ππN channels are represented by an effective σN channel, and we compare the case where the σ and π masses are related by m
σ = 2m
π and no width is considered, to another where the mass and width of the σ -meson are taken from ππ scattering data. The np → ηd cross-section can be well described up to about 60MeV by models where the real part of the ηN scattering length lies between 0.4≤Re(a
ηN)≤0.6 fm which allows us to determine the s -wave ηN scattering amplitude for -60≤E≤60 MeV. 相似文献
18.
We consider continuous-spin models on the d-dimensional hypercubic lattice with the spins σ
x
a priori uniformly distributed over the unit sphere in ℝ
n
(with n≥2) and the interaction energy having two parts: a short-range part, represented by a potential Φ, and a long-range antiferromagnetic
part λ|x−y|−s
σ
x
⋅σ
y
for some exponent s>d and λ≥0. We assume that Φ is twice continuously differentiable, finite range and invariant under rigid rotations of all spins.
For d≥1, s∈(d,d+2] and any λ>0, we then show that the expectation of each σ
x
vanishes in all translation-invariant Gibbs states. In particular, the spontaneous magnetization is zero and block-spin averages
vanish in all (translation invariant or not) Gibbs states. This contrasts the situation of λ=0 where the ferromagnetic nearest-neighbor systems in d≥3 exhibit strong magnetic order at sufficiently low temperatures. Our theorem extends an earlier result of A. van Enter ruling
out magnetized states with uniformly positive two-point correlation functions. 相似文献
19.
We investigate classical spin systems in d ≥ 1 dimensions whose transfer operator commutes with the action of a nonamenable unitary representation of a symmetry group,
here SO(1,N); these systems may alternatively be interpreted as systems of interacting quantum mechanical particles moving on hyperbolic
spaces. In sharp contrast to the analogous situation with a compact symmetry group the following results are found and proven:
(i) Spontaneous symmetry breaking already takes place for finite spatial volume/finitely many particles and even in dimensions
d = 1,2. The tuning of a coupling/temperature parameter cannot prevent the symmetry breaking. (ii) The systems have infinitely
many non-invariant and non-normalizable generalized ground states. (iii) The linear space spanned by these ground states carries
a distinguished unitary representation of SO(1, N), the limit of the spherical principal series. (iv) The properties (i)–(iii) hold universally, irrespective of the details
of the interaction.
Membre du CNRS 相似文献
20.
Guillaume Aubrun 《Communications in Mathematical Physics》2009,288(3):1103-1116
For large d, we study quantum channels on C
d
obtained by selecting randomly N independent Kraus operators according to a probability measure μ on the unitary group . When μ is the Haar measure, we show that for , such a channel is ε-randomizing with high probability, which means that it maps every state within distance ε/d (in operator norm) of the maximally mixed state. This slightly improves on a result by Hayden, Leung, Shor and Winter by
optimizing their discretization argument.
Moreover, for general μ, we obtain an ε-randomizing channel provided . For d = 2
k
(k qubits), this includes Kraus operators obtained by tensoring k random Pauli matrices. This leads to more efficient constructions of almost randomizing channels. The proof uses recent results
on empirical processes in Banach spaces. 相似文献