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排序方式: 共有84条查询结果,搜索用时 15 毫秒
1.
2.
Beyer RL Hoang HN Appleton TG Fairlie DP 《Journal of the American Chemical Society》2004,126(46):15096-15105
Short peptides corresponding to two to four alpha-helical turns of proteins are not thermodynamically stable helices in water. Unstructured octapeptide Ac-His1-Ala2-Ala3-His4-His5-Glu6-Leu7-His8-NH(2) (1) reacts with two [Pd((15)NH(2)(CH(2))(2)(15)NH(2))(NO(3))(2)] in water to form a kinetically stable intermediate, [[Pden](2)[(1,4)(5,8)-peptide]](2), in which two 19-membered metallocyclic rings stabilize two peptide turns. Slow subsequent folding to a thermodynamically more stable two-turn alpha-helix drives the equilibrium to [[Pden](2)[(1,5)(4,8)-peptide]] (3), featuring two 22-membered rings. This transformation from unstructured peptide via turns to an alpha-helix suggests that metal clips might be useful probes for investigating peptide folding. 相似文献
3.
4.
In this paper,we study the surface instability of a cylindrical pore in the absence of stress. This instability is called the Rayleigh-Plateau instabilty. We consider the model developed by Spencer et ... 相似文献
5.
Ebraheem Abdu Musad Saleh Abdullah Mohammed AL Dawsari Kakul Husain Ismail Hassan Kutty K.M.Lokanatha Rai 《Molecules (Basel, Switzerland)》2021,26(2)
A novel synthesis of thiazolo[2,3-b]quinazolines 4(a–e), pyrido[2′,3′:4,5]thiazolo[2,3-b]quinazolines {5(a–e), 6(a–e), and 7(a–e)}, pyrano[2′,3′:4,5]thiazolo[2,3-b]quinazolines 8(a–e), and benzo[4,5]thiazolo[2,3-b]quinazoloine9(a–e) derivatives starting from 2-(Bis-methylsulfanyl-methylene)-5,5-dimethyl-cyclohexane-1,3-dione 2 as efficient α,α dioxoketen dithioacetal is reported and the synthetic approaches of these types of compounds will provide an innovative molecular framework to the designing of new active heterocyclic compounds. In our study, we also present optimization of the synthetic method along with a biological evaluation of these newly synthesized compounds as antioxidants and antibacterial agents against the bacterial strains, like S. aureus, E. coli, and P. aeruginosa. Among all the evaluated compounds, it was found that some showed significant antioxidant activity at 10 μg/mL while the others exhibited better antibacterial activity at 100 μg/mL. The results of this study showed that compound 6(c) possessed remarkable antibacterial activity, whereas compound 9(c) exhibited the highest efficacy as an antioxidant. The structures of the new synthetic compounds were elucidated by elemental analysis, IR, 1H-NMR, and 13C-NMR. 相似文献
6.
D. R. Appleton 《The Journal of the Operational Research Society》1973,24(1):19-25
An interactive computer model of room usage in a university was designed and constructed in order to study limitations imposed on student numbers by existing accommodation, to allocate rooms efficiently to classes and to plan new buildings. 相似文献
7.
Gomez L Slutzky C Ferron J de La Figuera J Camarero J Vazquez De Parga AL de Miguel JJ Miranda R 《Physical review letters》2000,84(19):4397-4400
Generic computer simulations using empiric interatomic potentials suggest a new, collective mechanism that could be responsible for mixing at heteroepitaxial interfaces. Even if single adsorbate atoms diffuse by hopping on the substrate surface and do not mix at the terraces, two-dimensional islands formed by nucleation may become unstable above a certain critical size and explode upwards forming clusters of several atomic layers. This process is accompanied by strong distortions of the underlying atomic layers, and on soft materials it can result in surface etching and incorporation of substrate atoms into the islands. 相似文献
8.
9.
The reaction of cis-[Pt(15NH3)2(H2O) 2] 2+ (3) with N-acetylcysteine [H3accys] was investigated in aqueous solution. In this reaction, the ammine in the platinum complex formed was liberated. A
mono-dentate sulfur-boundplatinum(II) product cis-[Pt(15NH3)2(H2O)(H2accys-S)]+ (7) and six-membered che-late ring complex cis-[Pt(15NH3)2 (Haccys-S,O)] (8) were formed in solution. The dinuclear sulfur-bridged complex 9, giving a broad peak in 15N NMR, was also observed, but only present in very tiny amounts. The mass spectrometry (ES-MS) was undertaken from this re
action, and the product detected was only the dinuclear sulfur bridged platinum species and species related to it by ammine
loss. 相似文献
10.
Summary A theoretical and experimental investigation of the limitation on shock tube test times which is caused by the development of laminar and turbulent boundary layers behind the incident shock is presented. Two theoretical methods of predicting the test time have been developed. In the first a linearised solution of the unsteady one-dimensional conservation equations is obtained which describes the variations in the average flow properties external to the boundary layer. The boundary layer growth behind the shock is related to the actual extent of the hot flow and not, as in previous unsteady analyses, to its ideal extent. This new unsteady analysis is consequently not restricted to regions close to the diaphragm. Shock tube test times are determined from calculations of the perturbed shock and interface trajectories. In the second method a constant velocity shock is assumed and test times are determined by approximately satisfying only the condition of mass continuity between the shock and the interface. A critical comparison is made between this and previous theories which assume a constant velocity shock. Test times predicted by the constant shock speed theory are generally in agreement with those predicted by the unsteady theory, although the latter predicts a transient maximum test time in excess of the final asymptotic value. Shock tube test times have also been measured over a wide range of operating conditions and these measurements, supplemented by those reported elsewhere, are compared with the predictions of the theories; good agreement is generally obtained. Finally, a simple method of estimating shock tube test times is outlined, based on self similar solutions of the constant shock speed analysis.Nomenclature
a
speed of sound
-
A, B, C
constants defined in section 5.3
-
D
shock tube diameter
-
K
=/q
m, boundary layer growth constant, see Appendices A and B
-
l
hot flow length
-
m
constant, =1/2 or 4/5 for laminar or turbulent boundary layers, respectively
-
M
0
initial shock Mach number at the diaphragm
-
M
s
shock Mach number at station x
s
-
M
2
=(U
0–u
2)/a
2, hot flow Mach number relative to the shock front
-
N
=
2
a
2/
3
a
3, the ratio of acoustic impedances across the interface
-
P
pressure
-
P*
=P
e–P
2, perturbation pressure
-
q
boundary layer growth coordinate defined in § 2
-
Q
=(W–1+S) K
-
r
radial distance from shock tube axis
-
S
boundary layer integral defined by equation A6
-
t
time
- t
=/
, dimensionless ratio of test times
-
T
=l/l
, Roshko's dimensionless ratio of hot flow lengths
-
u
axial flow velocity in laboratory coordinate system, see figure 1a
-
u*
=u
e–u2, perturbation axial flow velocity
-
U
shock velocity
-
U
0
initial shock velocity at the diaphragm
-
U*
=U–U
0, perturbation shock velocity
-
v
axial flow velocity in shock-fixed coordinate system, see figure 1b
-
w
radial flow velocity
-
W
=U
0/(U
0–u
2), density ratio across the shock
-
x
axial distance from shock tube diaphragm
-
x
s, x
s
axial distance between shock wave and diaphragm
-
t
=
I/
, dimensionless ratio of test times
-
X
=l
I/l
, Roshko's dimensionless ratio of hot flow lengths
-
y
=(D/2)–r, radial distance from the shock tube wall
-
ratio of specific heats
-
boundary layer thickness; undefined
-
boundary layer displacement thickness
-
boundary layer thickness defined by equation A2
-
characteristic direction defined by dx/dt = (u
2–a
2)
-
=(M
0
2
+1)/(M
0
2
–1)
-
viscosity
-
characteristic direction defined by dx/dt=(u
2+a
2)
-
density
-
*
=
te–2, perturbation density
-
Prandtl number
-
shock tube test time
-
=M
0
2
/(M
0
2
–1)
Suffices 1
conditions in the undisturbed flow ahead of the shock
- 2
conditions immediately behind an unattenuated shock
- 3
conditions in the expanded driver gas
- 4
conditions in the undisturbed driver gas
-
e
conditions between the shock and the interface, averaged across the inviscid core flow
- i
conditions at the interface
- I
denotes the predictions of ideal shock tube theory
-
asymptotic conditions given when x
s and t
- s
conditions at or immediately behind the shock
- w
conditions at the shock tube wall
-
a, b, b
1, c, d, d
1, f, f
1, g, g
1, j, k, k
1
conditions at the points indicated in figure 2 相似文献