High frequency trading,liquidity, and execution cost

We build a model under the framework of discrete optimization to explain how high frequency trading (HFT) can be applied to supply liquidity and reduce execution cost. We derive the analytical properties of our model in finding the optimal solution to minimize the overall execution cost of HFT. We show that the execution cost can be reduced after increasing trading frequency (i.e., the higher the trading frequency, the lower the execution cost) with a simulation study. In addition, we conduct an empirical investigation with tick level data from US equity market through January 2008 to October 2010 to verify our conclusion drawn from the simulation study. Based on the simulation and empirical results we collected, we show that the HFT can reduce the execution cost when supplying liquidity.     

In vitro phase I metabolism of the depsipeptide enniatin B

The enniatins are a group of more than 20 cyclic depsipeptides from fungi with numerous biological effects. Enniatin B is commonly one of the principal analogues in species of the genus Fusarium, known to have ionophoric, antibiotic and insecticidal activity. In the present study, enniatin B was incubated with rat, dog and human liver microsomes. The compound was extensively metabolised, and 12 biotransformation products (M1–M12) were detected and their structures tentatively identified using a combination of mass spectrometric techniques and chemical derivatisation. Ion trap mass spectrometry, multiple-stage MS ⁿ fragmentation and high-resolution mass spectrometry were the instrumental backbone for structural determination, while acetylation, methylation and Jones oxidation were useful derivatisation techniques for the localisation of the site of biotransformation. Comparison of mass spectrometric data of the metabolism products with that of enniatin B suggested that M1–M5 are monohydroxylated species, while M8–M12 are the result of multiple oxidations (oxygenation and dehydrogenation). Metabolites M6 and M7 appeared to be enniatin B homologues and are the result of N-demethylation. Our findings show that oxidation and N-demethylation are the principal metabolic pathways in enniatin B phase I metabolism.     

Structural analysis of synthetic homo- and copolyesters by electrospray ionization on a fourier transform ion cyclotron resonance mass spectrometer

The molecular structure of a series of homo- and copolyesters was studied using sustained off-resonance irradiation collisionally activation dissociation on a Fourier transform ion cyclotron resonance mass spectrometer. Electrospray ionization was used as an ionization technique. The most important fragmentation pathways of the homopolyesters poly(dipropoxylated bisphenol-A/adipic acid) and poly(dipropoxylated bisphenol-A/isophthalic acid) were studied. Six different dissociation mechanisms were observed which are very similar to the mechanisms found to occur during pyrolysis of these compounds. Four of these mechanisms are a result of cleavages of the ester bond and the others are due to cleavages of the ether bond or bisphenol-A unit. Some of the fragments expected are not present in the spectrum, indicating that each fragment has a specific sodium affinity. Sequence-specific fragments of two of the three copolyester sequences that theoretically can exist were experimentally observed. Fragments that originate from the third sequence are not unique and can also be formed from other sequences. Therefore, it was not possible to determine the presence of the third sequence. Copyright 2000 John Wiley & Sons, Ltd.     

Cannabinoid CB1 receptor antagonists in therapeutic and structural perspectives

The observed antiobesity effect of rimonabant ( 1 ) in a pharmacological rodent model 10 years ago has led to a surge in the search for novel cannabinoid CB₁ antagonists as a new therapeutic target for the treatment of obesity. Rimonabant showed clinical efficacy in the treatment of obesity and also improved cardiovascular and metabolic risk factors. Cannabinoid CB₁ receptor antagonists have also good prospects in other therapeutic areas, including smoking and alcohol addiction as well as cognitive impairment. Solvay's research achievements in this fast‐moving field are reported in relation with the current state of the art. Several medicinal chemistry strategies have been pursued. The application of the concept of conformational constraint led to the discovery of more rigid analogs of the prototypic CB₁ receptor antagonist rimonabant. Replacement of the central heterocyclic pyrazole ring in rimonabant yielded imidazoles, triazoles, and thiazoles as selective CB₁ receptor antagonists. Dedicated medium‐throughput screening efforts delivered one 3,4‐diarylpyrazoline hit. Its poor pharmacokinetic properties were successfully optimized which led to the discovery of orally active and highly CB₁/CB₂ receptor selective analogs in this series. Regioisomeric 1,5‐diarylpyrazolines, 1,2‐diarylimidazolines, and water‐soluble imidazoles have been designed as novel CB₁ receptor antagonist structure classes. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 156–168; 2008: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20147     

b 1Σ+ Emissions from group V–VII diatomic molecules: bO+ → X1 O+ emission of Pl

Chemilluminescence of the bO⁺ → X₁O⁺ band system of P1 has been observed in a discharge flow system. Thirty-eight bands of the sequences, δν = +2, +1, 0, ?1, ?2 and ?3 were recorded photoelectrically at medium resolution. Evidence is presented that the vibrational numering assigned to the bands in the recently published first analysis of this system has to be modified. The re-analysis leads to the new constants (in cm ^?1) T_e = 11135 ± 5, ω′_e 400 ± 2, ω_e′_e = 1.4 ± 0.3, ω″_e = 372 ±2 and ωχ″_e, 1.4 ± 0.3 for the bO⁺ and χ₁ states, respectively. An upper limit of 0.01 was found for the ratio of the (0.0) band intensifies of the two sub-systems bO⁺ → χ₂ 1 and bO⁺ → χ₁O⁺.     

隐函数曲面的实时采样与三角化技术

采用逐步蔓延采样点和三角形的方法，给出了3个算法用于隐函数曲面的采样和三角化，这些算法使得隐函数曲面的重复绘制和控制都能实时进行，其采样方法具有局部适应性，能随着曲率的变化自动控制采样点的疏密程度，从而使得采样点尽量少，但又不至于遗漏表面细节，提出的三角化方法能用于其它散乱数据点的表面重构，它的算法复杂度仅为O(n)。