Envelope Forms Research Articles

An application of the Random Forest algorithm for the prediction of Solar Envelope ‘Floor Space Index’ based on spatiotemporal parameters

It is becoming increasingly important to consider access to the sun in the early stages of a new building's design process. A Solar Envelope is an architectural form that meets required levels of density, whilst also assuring solar access to neighbourhood surfaces, thereby making it feasible to implement active and passive solar technologies there. This preliminary study investigated the cross-cutting intersection between urban morphology, Solar Envelope forms, and a Random Forest algorithm to predict the Solar Envelope's Floor Space Index. Recognizing that Solar Envelope forms depend on various spatiotemporal contexts, mainly the solar exposure cut-off period (equinoxes/solstices) and various neighbourhood geometrical attributes, simulations varying only the rooftop typologies (flat, gable, hip, sled, mansard, and pyramid) and façade orientations (south, east, west, and north) were conducted to evaluate how solar access to those surfaces affect the Floor Space Index of the Solar Envelope. Architectural tools were used to conduct simulations reflecting varying spatiotemporal scenarios. The data was extracted and represented geometrically, involving polar loci, and this synthetic dataset was subsequently utilized to train and evaluate a Random Forest algorithm. The results of this study show that the Random Forest algorithm was able to predict the Floor Space Index of the Solar Envelope with about 90.18% accuracy, though the only parameter influencing the regression model was the solar exposure cut-off period and not any other morphological features. Therefore, the study sheds insight into the need for the development of a more robust dataset through the simulation of randomized and diversified neighbourhood morphologies.

Eclipse timing variations in post-common envelope binaries: Are they a reliable indicator of circumbinary companions?

ABSTRACT Post-common envelope binary systems evolve when matter is transferred from the primary star at a rate that cannot be accommodated by its secondary companion. A common envelope forms, which is subsequently ejected resulting in a system with a binary period frequently between 2 and 3 h. Where circumbinary companions are predicted, it remains unclear whether they form before or after the common envelope ejection. From observations of eclipse timing variations (ETVs), exoplanet data bases e.g. NASA Exoplanet Archive, list typically a dozen systems with confirmed circumbinary planets. Here, we examine seven of these systems, discuss other possible causes, and consider whether, for these dynamic systems, the ETV methodology is a reliable indicator of planetary companions. The systems selected were those where we could determine precise eclipse timings, free from significant extraneous effects such as pulsations, and present 163 new times of minima permitting us to test existing models. Over 30 circumbinary models have been proposed for these seven systems and note that all, other than the latest model for NY Vir, which remains to be fully tested, fail within a year to accurately predict eclipse times. In examining alternative mechanisms, we find that magnetic effects could contribute significantly in two of the seven systems studied. We conclude that the structure of these dynamic systems, with the extreme temperature differences and small binary separations, is not fully understood and that many factors may contribute to the observed ETVs.

Spin dynamics of a hydrogen atom in a periodic magnetic structure

The spin dynamics of a hydrogen atom during the passage of a periodic magnetic structure is discussed. The occupation numbers of the components of the hyperfine structure are considered as a function of time. The characteristic low-frequency oscillations are visible, which have a direct analogue in the effect of nuclear magnetic resonance. An envelope forms of these oscillations are found using the Krylov–Bogolyubov–Mitropol’skii method. The dependence of spin dynamics on the parameters of the magnetic structure is investigated. It is shown that this dependence is very sensitive to the structure of the magnetic field.

Comparison and Use of Failure Envelope Forms for Slope Stability Analyses

This paper reviews and compares different mathematical forms for representing the effective stress failure envelope in the context of slope stability analysis. Although commonly assumed to be linear, the effective stress failure envelope for many soils is non-linear, at least when considered over a wide range of normal stresses. Multiple studies have considered the effects of including non-linearity in slope stability calculations, but little guidance is available for selecting an appropriate envelope form. Differences between six mathematical forms are examined by analyzing four real data sets, each with different characteristics. Statistical descriptors are used to evaluate the goodness of fit for each form. Two simple slopes are analyzed with each data set to ascertain the impact that the envelope form has on the calculated factor of safety. The envelope form is shown to have a relatively small impact on the predicted shear strength and calculated factor of safety for slope stability, provided that (1) the failure envelopes are fit to the test data using a robust regression procedure and (2) the effective normal stresses acting on the critical failure surface are mostly within the range tested by the laboratory shear strength program. The largest differences in predicted shear strength occurred when the failure envelopes were extrapolated to stresses below the laboratory test stress range. In this low stress range, a practical engineering solution is obtained by drawing a linear failure envelope from the origin to the “best-fit” failure envelope at the lowest effective normal stress indicated by the test data.

Interaction of Arsenous Acid with the Dithiol-Type Chelator British Anti-Lewisite (BAL): Structure and Stability of Species Formed in an Unexpectedly Complex System.

British anti-Lewisite (2,3-dimerkaptopropan-1-ol, dimercaprol, BAL) is one of the best-known chelator-type therapeutic agents against toxic metal ions and metalloids, especially arsenicals. Surprisingly, the mechanisms of action at the molecular level, as well as the coordination features of this traditional drug toward various arsenicals, are still poorly revealed. The present study on the interaction of arsenous acid (H3AsO3) with BAL, involving UV and NMR titrations, electrospray ionization mass spectrometry, and 2D NMR experiments combined with MP2 calculations, demonstrates that the reaction of H3AsO3 with BAL at pH = 7.0 results in a more complex speciation than was assumed before. The three reactive hydroxyl groups of H3AsO3 allow for interaction with three thiol moieties via condensation reaction, leading to the observed AsBAL2 and As2BAL3 complexes besides the AsBAL species. This indicates the strong propensity of inorganic As(III) to saturate its coordination sphere with thiolate groups. The alcoholic hydroxyl group of the ligand may also directly bind to As(III) in AsBAL. Compared to dithiothreitol or dithioeritritol, the preference of BAL to form complexes with such a tridentate binding mode is much lower owing to the more strained bridged bicyclic structure with an αAsSC < 90° bond angle and an unfavorable condensed boat-type six-membered ring. On the basis of the NMR data, the predominating, bidentately bound AsBAL species, including a five-membered chelate ring, exists in rapidly interconverting envelope forms of E and Z stereoisomers. The conditional stability constants calculated for the three macrospecies from a series of UV data [log βpH=7.0 = 6.95 (AsBAL), 11.56 (AsBAL2), and 22.73 (As2BAL3)] reflect that BAL is still the most efficient, known, dithiol-type chelator of H3AsO3.

Crystal structure of (-)-(5R,7R,8S,9R,10S)-8-methyl-7-[(5R)-3-methyl-2-oxooxolan-3-en-5-yl]-1-aza-6-oxatri-cyclo-[8.3.0.05,9]tridecan-13-one monohydrate.

The title compound, C17H23NO4·H2O, is an epimer of the natural tetra-cyclic alkaloid isosaxorumamide which consists of a fused 5-7-5 tricyclic core and a di-hydro-furan-one substituent. The terminal di-hydro-furan ring is essentially planar with a maximum deviation of 0.0273 (14) Å from the mean plane and oxolane, azepane and pyrrolidine rings in the tricyclic ring system adopt twist, twist-chair and envelope forms, respectively. In the crystal, the amide and water mol-ecules are linked by O-H⋯O hydrogen bonds, forming a tape structure running along the b-axis direction. The tapes are further connected by C-H⋯O inter-actions into a three-dimensional architecture.

The impact of the Hall effect during cloud core collapse: Implications for circumstellar disk evolution

Abstract We perform three-dimensional radiation non-ideal magnetohydrodynamics simulations and investigate the impact of the Hall effect on the angular momentum evolution in collapsing cloud cores in which the magnetic field B and angular momentum Jang are misaligned with each other. We find that the Hall effect noticeably changes the magnetic torques in the pseudo-disk, and strengthens and weakens the magnetic braking in cores with acute and obtuse relative angles between B and Jang, respectively. This suggests that the bimodal evolution of the disk size may occur in the early disk evolutionary phase even if B and Jang are randomly distributed. We show that a counter-rotating envelope forms in the upper envelope of the pseudo-disk in cloud cores with obtuse relative angles. We also find that a counter-rotating region forms at the midplane of the pseudo-disk in cloud cores with acute relative angles. The former and latter types of counter-rotating envelopes may be associated with young stellar objects with large (r ∼ 100 au) and small (r ≲ 10 au) disks, respectively.

The virtual aeroshaping enhancement by synthetic jets with variable suction and blowing cycles

A novel waveform modified from the standard-sinusoidal function is adopted to enhance the virtual aeroshaping effect of the synthetic jets positioned at the front stagnation point of a circular cylinder. The waveform is characterized by a control parameter, namely, the suction duty cycle factor k, which is the ratio of the time duration of the suction cycle to that of the blowing cycle. The strength of the synthetic jet vortex pair is enhanced by increasing the suction duty cycle factor. The periodic closed envelope forms upstream of the circular cylinder for k ≤ 1.00, while the quasi-steady open envelope forms for k ≥ 2.00, acting the virtual aeroshaping effect. As a result, both the statistical characteristics and the vortex dynamics of the near-wake flow field change with the suction duty cycle factor. The recirculation region downstream of the circular cylinder becomes smaller or even disappears, and thus, the drag coefficient over the circular cylinder is reduced by increasing the suction duty cycle factor to k ≥ 1.00. The statistical mean and fluctuating velocities show corresponding changes in the near wake with the different wake patterns. For k ≤ 0.50, the wake vortex shows the antisymmetric shedding mode which is similar with the natural case. For 1.00 ≤ k ≤ 2.00, the wake vortex shows the bistable state mode, where vortex sheds with symmetric or antisymmetric mode; the antisymmetric shedding mode dominates the global flow field for k = 1.00, while it is the symmetric shedding mode that dominates the flow field for k = 2.00. For k = 4.00, it shows the antisymmetric shedding mode with a shorter vortex formation length than the natural case. The above findings indicate that the virtual aeroshaping effect of the synthetic jets can be enhanced by increasing the suction duty cycle factor so as to increase the momentum coefficient while keeping other control parameters unchanged, providing us another way for effective flow control.

Types of gaseous envelopes of “hot Jupiter” exoplanets

As a rule, the orbital velocities of "hot Jupiters," i.e., exoplanets with masses comparable to the mass of Jupiter and orbital semi-major axes less than 0.1 AU, are supersonic relative to the stellar wind, resulting in the formation of a bow shock. Gas-dynamical modeling shows that the gaseous envelopes around "hot Jupiters" can belong to two classes, depending on the position of the collision point. if the collision point is inside the Roche lobe of the planet, the envelopes have the almost spherical shapes of classical atmospheres, slightly distorted by the influence of the star and interactions with the stellar-wind gas; if the collision point is located outside the Roche lobe, outflows from the vicinity of the Lagrangian points $\mathrm L_1$ and $\mathrm L_2$ arise, and the envelope becomes substantially asymmetrical. The latter class of objects can also be divided into two types. If the dynamical pressure of the stellar-wind gas is high enough to stop the most powerful outflow from the vicinity of the inner Lagrangian point $\mathrm L_1$, a closed quasi-spherical envelope with a complex shape forms in the system. If the wind is unable to stop the outflow from $\mathrm L_1$, an open aspherical envelope forms. The possible existence of atmospheres of these three types is confirmed by 3D numerical modeling. Using the typical "hot Jupiter" HD 209458b as an example, it is shown that all three types of atmospheres could exist within the range of estimated parameters of this planet. Since different types of envelopes have different observational manifestations, determining the type of envelope in HD 209458b could apply additional constrains on the parameters of this exoplanet.

Hydrogen-bonded bilayers in 7-benzyl-3-tert-butyl-1-phenyl-4,5,6,7-tetrahydro-1H-spiro[pyrazolo[3,4-b]pyridine-5,2′-indan]-1′,3′-dione

In the title compound, C₃₁H₂₉N₃O₂, the reduced pyridine ring adopts a conformation intermediate between the envelope and half-chair forms. The aryl rings of the benzyl and phenyl substituents are nearly parallel and overlap, indicative of an intramolecular π-π stacking interaction. A combination of two C-H∙∙∙O hydrogen bonds and one C-H∙∙∙N hydrogen bond links the molecules into a bilayer having tert-butyl groups on both faces.

(25R)-6α-Hydroxy-5α-spirostan-3β-yl tosylate

The title steroid, C34H50O6S, is an inter­mediate on the synthetic route between diosgenin and brassinosteroids, which possess the A ring modified with the 2α,3α-diol functionality. The polycyclic spiro­stan system has the expected conformation, with six-membered rings adopting chair forms and the five-membered rings envelope forms (flap atoms are the methine C atom in the C/D-ring junction and the spiro C atom connecting rings E and F). The 3β-tosyl­ate group is oriented in such a way that S=O bonds are engaged in inter­molecular hydrogen bonds with O—H and C—H donors. Chains of mol­ecules are formed along [100] via O—H⋯O hydrogen bonds, and secondary weak C—H⋯O inter­actions connect two neighbouring chains in the [001] direction.

Crystal Structure Analysis and Antinociceptive Property of Lappaconitine Hydrochloride

An alkaloid compound, lappaconitine Hydrochloride, was synthesized with lappaconitine which was isolated from the root ofAconitum sinomontanum Nakaiin Gansu province in China. The structures were elucidated by IR,NMR, Anal. and X-ray diffraction analysis. Crystal data: C32H47ClN2O9,Mr= 639.17, space group monoclinic, P21; a=10.665 (7) Å, b=12.178 (7) Å and c=12.214 (7) Å; β=91.003 (10)°, Z=2, Dx= 1.338 mg/m-3,F(000)= 684,µ=0.18.00 mm-1, V=1586.1 (16) Å3; R1=0.038,wR2=0.087, Flack parameter x= -0.12 (7). RingA, B, C, D, EandFrespectively present boat, chair, envelope, boat, boat and envelope forms. The absolute configuration was determined as 1S, 4S, 5S, 7S, 8S, 9S, 10S, 11S, 13R, 14S, 16S, 17 R. And the analgesic potential has been investigated in a mouse model of acute pain. The result exhibited that the analgesic effect of the compound is worse than lappaconitine hydrobromide.

Formation of the postmitotic nuclear envelope from extended ER cisternae precedes nuclear pore assembly

During mitosis, the nuclear envelope merges with the endoplasmic reticulum (ER), and nuclear pore complexes are disassembled. In a current model for reassembly after mitosis, the nuclear envelope forms by a reshaping of ER tubules. For the assembly of pores, two major models have been proposed. In the insertion model, nuclear pore complexes are embedded in the nuclear envelope after their formation. In the prepore model, nucleoporins assemble on the chromatin as an intermediate nuclear pore complex before nuclear envelope formation. Using live-cell imaging and electron microscope tomography, we find that the mitotic assembly of the nuclear envelope primarily originates from ER cisternae. Moreover, the nuclear pore complexes assemble only on the already formed nuclear envelope. Indeed, all the chromatin-associated Nup107-160 complexes are in single units instead of assembled prepores. We therefore propose that the postmitotic nuclear envelope assembles directly from ER cisternae followed by membrane-dependent insertion of nuclear pore complexes.

(Z)-3α-(1,3-Dioxoisoindolin-2-yl)-17(20)-pregnene

The title compound, C29H37NO2, crystallized with two independent mol­ecules in an asymmetric unit in which the conformation of the cyclo­hexyl ring of the pregnene moiety bonded to the 3α-(1,3-dioxoisoindolin-2-yl)- ring system differs: in one mol­ecule it is in a chair conformation, while in the other it exhibits a half-chair conformation. The other six-membered rings in the pregnene moiety are in chair conformations and the five-membered rings are in envelope forms in both mol­ecules. In both mol­ecules, the 3α-(1,3-dioxoisoindolin-2-yl)- ring systems are individually approximately planar, with r.m.s. devtaions 0.0148 and 0.0264 Å. The structure is consolidated by inter­molecular C—H⋯O hydrogen-bonding inter­actions involving the carbonyl O atoms and methyl, methyl­ene and methyl­idyne groups, resulting in a two-dimensional structure.

Infrared and Raman spectra, ab initio calculations, conformational stability and vibrational assignment of 1-bromo-1-silacyclopentane

Infrared and Raman spectra (3500–60 cm −1) of gas and/or liquid and solid 1-bromo-1-silacyclopentane (c-C 4H 8SiBrH) have been recorded and the vibrational data indicate the presence of a single conformer with no symmetry which is consistent with the twisted form. Ab initio calculations with a variety of basis sets up to MP2(full)/6-311+G(2df,2pd) predict the envelope-axial and envelope-equatorial conformers to be saddle points with nearly the same energies but approximately 900 cm −1 (5.98 kJ/mol) lower in energy than the planar conformer. Density functional theory calculations by the B3LYP method predict slightly lower energies for the two envelope forms and considerably lower energy for the planar form compared to the MP2 predictions. By utilizing the MP2(full)/6-31G(d) calculations the force constants, frequencies, infrared intensities, band contours, Raman activities, and depolarization values have been obtained to support the vibrational assignment. Estimated r 0 structural parameters have been obtained from adjusted MP2(full)/6-311+G(d,p) calculations. These experimental and theoretical results are compared to the corresponding quantities of some other five-membered rings.

Infrared and Raman spectra, conformational stability and vibrational assignment of 1-chloro-1-silacyclopentane

Infrared and Raman spectra (3500–60cm−1) of gas and/or liquid and solid 1-chloro-1-silacyclopentane (c-C4H8SiClH) have been recorded and the vibrational data indicate the presence of a single conformer with no symmetry which is consistent with the twisted form. Ab initio calculations with a variety of basis sets up to MP2(full)/aug-cc-pVTZ predict the envelope-axial and envelope-equatorial conformers are saddle points with nearly the same energies but much lower in energy than the planar conformer. Density functional theory calculations by the B3LYP method predicts slightly lower energies for the two envelope forms and considerably lower for the planar form. By utilizing the MP2(full)/6–31G(d) calculations the force constants, frequencies, infrared intensities, band contours, Raman activities, and depolarization values have been obtained to support the vibrational assignment. Estimated r0 structural parameters have been obtained from adjusted MP2(full)/6–311+G(d, p) calculations. These experimental and theoretical results are compared to the corresponding quantities of some other five-membered rings.

On the PPh3 catalyzed reaction between dibenzoylacetylene and vicinal -OH and -SH acids. One-pot synthesis of 1,3-dioxolane derivative

Abstract The efficient conjugate addition of vicinal - OH and - SH acids such as ethylene glycol and 1,2-ethanedithiol to dibenzoylacetylene in the presence of PPh3 leads to different products depending on the reaction conditions. Ab initio calculations at HF/6-31G* level shows that the unsymmetrical envelope conformation of 2,2-disubstituted 1,3-dioxolane 1 is more stable than the half-chair and Cs symmetric envelope forms.

X-ray structure analysis of lappaconitine

Lappaconitine is an important alkaloid of the aconite family and its biological activity is closely related to its structure. Through an X-ray structure analysis of hydrated lappaconitine hydrobromide, which was synthesised by us through a new method, the absolute configuration of lappaconitine was determined: monoclinic, P2 1 , a = 10.619(2) Å, b = 12.196(3) Å, c = 12.282(2) Å, β = 90.87(1)° and Z = 2; Flack parameter is −0.0083(0.0046) and S = 0.867. Rings A, B, C, D, E and F, respectively, present boat, chair, envelope, boat, boat and envelope forms. The absolute stereo configuration of lappaconitine was determined as 1S, 4S, 5S, 7S, 8S, 9S, 10S, 11S, 13R, 14S, 16S and 17R.

Conformational and configurational disorder in 6-(3,4,5-trimethoxyphenyl)-6,7-dihydro-5H-1,3-dioxolo[4,5-g]quinolin-8(5H)-one and 6-(1,3-benzodioxol-5-yl)-6,7-dihydro-5H-1,3-dioxolo[4,5-g]quinolin-8-one: a hydrogen-bonded chain of rings and π-stacked hydrogen-bonded chains

In 6-(3,4,5-trimethoxyphenyl)-6,7-dihydro-5H-1,3-dioxolo[4,5-g]quinolin-8(5H)-one, C(19)H(19)NO(6), (I), the six-membered heterocyclic ring adopts a conformation intermediate between envelope and half-chair forms; it is disordered over two enantiomeric configurations, with occupancies of 0.879 (3) and 0.121 (3), leading to positional disorder of the 3,4,5-trimethoxyphenyl unit. In 6-(1,3-benzodioxol-5-yl)-6,7-dihydro-5H-1,3-dioxolo[4,5-g]quinolin-8-one, C(17)H(13)NO(5), (II), the molecules are similarly disordered, with occupancies of 0.866 (4) and 0.134 (4). The molecules in (I) are linked by one three-centre N-H...(O)(2) hydrogen bond and one two-centre C-H...O hydrogen bond to form a complex chain of rings whose formation is reinforced by two independent aromatic pi-pi stacking interactions. In (II), a single N-H...O hydrogen bond links the molecules into a simple chain, and pairs of chains are linked by a single aromatic pi-pi stacking interaction.

Experimental investigations on separation control and flow structure around a circular cylinder with synthetic jet

Circular cylinder separation control and flow structure influenced by the synthetic jet have been experimentally investigated in a water channel. The synthetic jet issues from a slot and ejects toward upstream from the front stagnation point of the cylinder. It has been found that, similar to the traditional synthetic jet which is positioned near the separation point or inside the separation region, the present synthetic jet arrangement constitutes an efficient way to control flow separation of the circular cylinder, but with a different control mechanism. The present synthetic jet leads to an upstream displacement of the front stagnation point and the formation of a vortex pair near both sides of the exit orifice. When Re u based on the synthetic jet average exit orifice velocity is about lower than 43, a closed envelope forms in front of the windward side of the cylinder during the blowing cycle of synthetic jet, which acts as an apparent modification for the cylinder configuration. When Re u is high enough, an open envelope forms upstream of the cylinder, and the flow around the cylinder becomes much energetic. Thus, regardless of Re u, the present synthetic jet can improve separation for flow around a circular cylinder. With regard to the leeward side, as Re u increases, the flow separation region behind the cylinder gradually disappears. The flow over cylinder may be fully attached when the open envelope forms upstream of the cylinder and Re u is greater than 344. Then, the flow past the cylinder will converge near the back stagnation point of the cylinder, where a new vortex pair shedding periodically is generated due to the high shear layer.