Deliquescence and Efflorescence Processes of Aerosol Particles Studied by in situ FTIR and Raman Spectroscopy

Deliquescence and efflorescence are the two most important physicochemical processes of aerosol particles. In deliquescence and efflorescence cycles of aerosol particles, many fundamental problems need to be investigated in detail on the molecular level, including ion and molecule interactions in supersaturated aerosols, metastable solid phases that may be formed, and microscopic structures and deliquescence mechanisms of aerosol particles. This paper presents a summary of the progress made in recent investigations of deliquescence and efflorescence processes of aerosol particles by four common spectral techniques, which are known as Raman/electrodynamic balance, Fourier transform infrared/aerosol flow tube, Fourier transform infrared/attenuated total reftection, and confocal Raman on a quartz substrate.

A database for deliquescence and efflorescence relative humidities of compounds with atmospheric relevance

Deliquescence relative humidity(DRH)and efflorescence relative humidity(ERH),the two parameters that regulate phase state and hygroscopicity of substances,play important roles in atmospheric science and many other fields.A large number of experimental studies have measured the DRH and ERH values of compounds with atmospheric relevance,but these values have not yet been summarized in a comprehensive manner.In this work,we develop for the first-of-its-kind a comprehensive database which compiles the DRH and ERH values of 110 compounds(68 inorganics and 42 organics)measured in previous studies,provide the preferred DRH and ERH values at 298 K for these compounds,and discuss the effects of a few key factors(e.g,emperature and partile size)on the measured DRH and ERH values.In addition,we outline future work that will broaden the scope of this database and enhance its accessibility.

Impact of Solid / Vapour Equilibria on Conditions of Crystallization of Pharmaceutical Compounds

The influence of solvent (in its gaseous state) on the stability of crystallized organic compounds was investigated. Through two examples of studies on the solid/vapour equilibria made in our lab, several behaviors were highlighted: (i) a new hydrated phase (thermodynamically stable) of an active pharmaceutical ingredient (API) was detected after the recrystallization starting from a deliquescent state, (ii) a spontaneous resolution of a hydrated racemic compound towards an anhydrous conglomerate can occur during the desolvation under the precise conditions of temperature and humidity. This study illustrates that knowledge about solid/vapour equilibrium is a crucial step during the complete characterization of solid organic compounds.

A modified technique of bone grafting pedicled with femoral quadratus for alcohol-induced osteonecrosis of the femoral head

Background Quadratus femoris pedicled bone grafting has yielded satisfactory long-term clinical outcome for osteonecrosis of the femoral head （ONFH） in pre-collapse ONFH without extensive lesion. However, for pre-collapse ONFH with extensive necrotic area, it is still challenging to preserve the femoral head. The current study aimed to introduce a new technique of deliquesce strut with titanium mesh containing bone grafting pedicled with the femoral quadratus and to evaluate its short-term outcomes.Methods From January 2008 to December 2008, 10 ONFH patients （12 hips） underwent operations by a new technique of deliquesce strut with titanium mesh containing bone grafting pedicled with the femoral quadratus （group A）.According to the ARCO classification system, there were two hips in stage Ⅱ B and 10 hips in stage Ⅱ C. Also in the same period, 12 ONFH patients （16 hips） underwent operations by the conventional procedure of quadratus femoris pedicled bone grafting （group B）. There were 6 hips in stage Ⅱ B and 10 hips in stage Ⅱ C. All patients were males and suffered from alcohol induced ONFH. For the new technique, the necrotic area was evaluated, and a titanium mesh piece of the same size （range from 2.5 cm×2.8 cm to 2.8 cm×3.4 cm） was obtained and shaped to match the contour of the head. The cancellous bone was first placed underneath the subchondral bone and was densely impacted （about 1 to 2 mm thick）.Then the titanium mesh piece was inserted. The length of the decompressive trough was measured. A titanium cylinder mesh cage with a diameter of 1.6 cm of the same length was obtained, with a ＂U＂ shaped window in the wall being created to make room for the muscle pedicle. The muscle pedicle bone was inserted into the titanium mesh cage to form a bone graft-titanium cage complex and, then the complex was inserted. The hundred percent score method was used for outcome evaluation. Clinical and radiographic outcomes were compared between group A and group B.Results The average operative time was 150 minutes （130 to 185 minutes） in group A, with an average of 130 minutes （120 to 180 minutes） in group B. The mean blood loss was 400 ml （300 to 500 ml） in group Aand 350 ml （250 to 500 ml）in group B. Group A patients were followed up for an average of 19.2 months （14 to 24 months）, with an average of 18.5 months （12 to 24 months） for Group B. Full weight bearing was allowed 5 to 7 months postoperatively. Pain and function were obviously improved. For group A, pain score improved from a mean of 9.8 points preoperatively to an average of 24.6 points postoperatively, and function score improved from a mean of 9.0 points preoperatively to an average of 17.4 points postoperatively. In group B, pain score improved from a mean of 9.5 points preoperatively to an average of 24.2 points postoperatively and function score improved from a mean of 9.2 points preoperatively to an average of 17.2 points postoperatively. The range of motion changed the least, with score improvement from a preoperative mean of 13.9 points to postoperative 16.8 points for group A and from a preoperative mean of 13.7 points to postoperative 16.5 points for group B. Radiographic score improved from preoperative 31 points to postoperative 38 points for group A, in comparison with an improvement from preoperative 31 points to postoperative 37 points for group B. At the latest follow up, 11 hips were rated as excellent and 1 hip was better for group A, with 14 hips being rated as excellent and 2 hips being better in group B. There was no statistically significant difference between groups A and B in clinical and radiographic outcomes.Conclusion For ONFH in stage ARCO llC, satisfactory clinical outcome can be achieved by the new technique in the short-term period while the long-term clinical outcome has yet to be determined.

Hygroscopicity measurement of sodium carbonate,β-alanine and internally mixed β-alanine/Na2CO3 particles by ATR-FTIR

Water-uptakes of pure sodium carbonate(Na2CO3),pureβ-alanine and internally mixedβ-alanine/Na2CO3 aerosol particles with different mole ratios are first monitored using attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR)technique.For pure Na2CO3 aerosol particles,combining the absorptions at 877 and 1422 cm-1 with abrupt water loss shows the efflorescence relative humidity(ERH)of 62.9%–51.9%.Upon humidifying,solid Na2CO3 firstly absorbs water to from Na2CO3·H2O crystal at 72.0%RH and then deliquesces at 84.5%RH(DRH).As for pureβ-alanine particles,the crystallization takes place in the range of 42.4%–33.2%RH and becomes droplets at^88.2%RH.Whenβ-alanine is mixed with Na2CO3 at various mole ratios,it shows no efflorescence of Na2CO3 whenβ-alanine to Na2CO3 mole ratio(OIR)is 2:1.For 1:1 and 1:2β-alanine/Na2CO3 aerosols,the ERHs of Na2CO3 are 51.8%–42.3%and 57.1%–42.3%,respectively.Whileβ-alanine crystal appears from 62.7%RH for 2:1 and 59.4%RH for both 1:1 and 1:2 particles and lasts to driest state.On hydration,the DRH is 44.7%–75.2%for Na2CO3 with the OIR of 1:1 and 44.7%–69.0%for 1:2 mixture,and those of β-alanine are 74.8% for 2:1 mixture and 68.9%for two others.After the first dehumidification–humidification,all the water contents decrease despite of constituent fraction.And at^92%RH,the remaining water contents are 92%,89%and 82%at^92%RH,corresponding to OIR of 2:1,1:1 and 1:2 mixed system,respectively.

Experimental study on high-efficiency polishing for potassium dihydrogen phosphate (KDP) crystal by using two-phase air-water fluid

A high-efficiency polishing approach using two-phase air–water fluid(TAWF)is proposed to avoid surface contamination and solve the inefficiency of previous water-dissolution polishing techniques for potassium dihydrogen phosphate(KDP)crystal.In the proposed method,controllable deliquescence is implemented without any chemical impurity.The product of deliquescence is then removed by a polishing pad to achieve surface planarization.The mechanism underlying TAWF polishing is analyzed,a special device is built to polish the KDP crystal,and the effect of relative humidity(RH)on polishing performance is studied.The relationship between key parameters of polishing and surface planarization is also investigated.Results show that the polishing performance is improved with increasing RH.However,precisely controlling the RH is extremely difficult during TAWF polishing.Controllable deliquescence can easily be disrupted once the RH fluctuates,which therefore needs to be restricted to a low level to avoid its influence on deliquescence rate.The material removal of TAWF polishing is mainly attributed to the synergistic effect of deliquescence and the polishing pad.Excessive polishing pressure and revolution rate remarkably reduce the life of the polishing pad and the surface quality of the KDP crystal.TAWF polishing using IC-1000 and TEC-168S increase the machining efficiency by 150%,and a smooth surface with a root mean square surface roughness of 5.5 nm is obtained.