Experimental and theoretical justifications for the observed discriminations between enantiomers of prochiral alcohols by chirally blind EI-MS

To all appearances, electron impact mass spectrometer (EI-MS) is considered a "chirally blind" instrument. Yet, numerous non-identical R (right) and S (left) configurations of prochiral alcohols' mass spectra alcohols have appeared in the literature with almost no justification. Such observations are often attributed to impurities, experimental circumstances, inaccurate measurements, etc. In an experimental attempt to explain this phenomenon, here we have avoided the above mentioned pitfalls by conducting control experiments using different pure enantiomers under the same circumstances. Hence, we report the mass spectra of R- and S-enantiomers of 2-octanol (1R, 1S) and 1-octyn-3-ol (2R, 2S) collected by running 20 independent experiments for each R- and S-enantiomer. Statistical analyses confirmed that the peak intensities were significant to an acceptable level of confidence. The 1R and 1S enantiomers were separated reasonably in the PC space, implying that the chirally blind EI-MS is able to discriminate between R and S prochiral alcohols. Theoretically, self-complexation through H-bonding for S (or R) appears to give a new chiral center at the H-bonded oxygen atom, producing a new dimeric pair of diastereomers SRS and SSS (or RRR and RSR) before ionization, and SRS.+ and SSS.+ (or RRR.+ and RSR.+) after ionization. The results of our calculations have explicitly shown that these hydrogen bonds formed. Interestingly, the latter four ionized diastereomers appear with different structural and thermodynamic parameters at the M06-2X/6-311++g (d,p) level of theory

Comparison of the application of low concentration and 80% phenol solution in pilonidal sinus disease

Objectives Many conservative methods have been applied in the treatment of pilonidal sinus disease (PSD). The most commonly used conservative treatment is 80% phenol solution. Our observations demonstrated that 80% phenol solution caused much destruction in the sacrococcygeal region. Design In this study low concentrations of phenol were used with the aim of reducing the unwanted side-effects of high-concentration phenol without reducing the therapeutic effects. Participants We treated 112 patients (18 women, 94 men) with PSD using phenol solution. Patients were divided into two groups: Group A was treated with a 40% solution of phenol solution, and Group B was treated with an 80% solution of phenol solution. Setting All patients were treated on an outpatient basis. One mL of low (40%) or high (80%) concentration phenol solution was injected into the main sinus orifice. During the check it was observed and noted whether there was skin necrosis, fatty tissue necrosis or abscesses. Main outcome measures The mean age was 27.4 years (6–44). The median length of symptoms was seven months (0.5–132). In the 2.8 years (1–6) of mean follow-up period, the disease recurred in 13 (11.6%) patients. Results This treatment procedure was well-tolerated by all the patients except for those who had unwanted results. No patients in group A had skin necrosis, and only one had abscesses. In group B two patients had abscesses, and three had skin necrosis. Fatty tissue necrosis was seen in one patient in Group A and in five patients in Group B. Recurrence rates were four (7.4%) cases in Group A and nine (15.5%) cases in Group B. Conclusions It is possible to treat patients in a shorter time with a considerably smaller loss of working time, since the destruction of peripilonidal adipose tissue and skin is less. Therefore, the use of low-concentration phenol solution is an option to be considered in the treatment of PSD.PubMe

Preconditioning-induced ischemic tolerance: a window into endogenous gearing for cerebroprotection

Ischemic tolerance defines transient resistance to lethal ischemia gained by a prior sublethal noxious stimulus (i.e., preconditioning). This adaptive response is thought to be an evolutionarily conserved defense mechanism, observed in a wide variety of species. Preconditioning confers ischemic tolerance if not in all, in most organ systems, including the heart, kidney, liver, and small intestine. Since the first landmark experimental demonstration of ischemic tolerance in the gerbil brain in early 1990's, basic scientific knowledge on the mechanisms of cerebral ischemic tolerance increased substantially. Various noxious stimuli can precondition the brain, presumably through a common mechanism, genomic reprogramming. Ischemic tolerance occurs in two temporally distinct windows. Early tolerance can be achieved within minutes, but wanes also rapidly, within hours. Delayed tolerance develops in hours and lasts for days. The main mechanism involved in early tolerance is adaptation of membrane receptors, whereas gene activation with subsequent de novo protein synthesis dominates delayed tolerance. Ischemic preconditioning is associated with robust cerebroprotection in animals. In humans, transient ischemic attacks may be the clinical correlate of preconditioning leading to ischemic tolerance. Mimicking the mechanisms of this unique endogenous protection process is therefore a potential strategy for stroke prevention. Perhaps new remedies for stroke are very close, right in our cells

Stock markets and effective exchange rates in European countries: threshold cointegration findings

© 2015, Eurasia Business and Economics Society. The nexus between stock markets and exchange rates is examined in the case of eight European countries. The sample consists of four economies with national currencies and four that have adopted the euro. Thus, if differences between the two groups in the relationship governing the two markets exist, they will be unveiled. To this effect, a threshold cointegration methodology is adopted that allows for more reliable inferences to be drawn for both the short and long run nexus between the two markets. Monthly data is used covering the period 01/2000–12/2014. The findings reported herein offer support in favor of the portfolio approach thesis over the recent economic crisis period, but this finding is not the case for the entire sample. Bidirectional causality is found for Norway and the UK, pointing to a currency effect on stock markets. In view of the findings reported herein, policies aiming at reducing uncertainty in the stock markets can exert beneficial effects on currency markets

Mechanical Properties of Polyamide Versus Different PMMA Denture Base Materials

PubMedID: 22372855Purpose: Polymethyl methacrylate (PMMA) resins are the most commonly used denture materials; however, they do not have a high flexural strength (FS). This study aimed to compare the mechanical properties of a polyamide-based, injection-molded denture material (Deflex) with another injection-molded PMMA base material (SR-Ivocap) and a conventional compression-molded PMMA (Meliodent). Materials and Methods: Flexural properties (deflection, bending strength, and bending modulus) of denture base materials were evaluated (n = 10). Specimens meeting International Standards Organization (ISO) specification number 20795-1 requirements were prepared (65 × 10 × 3 mm 3). A three-point bending test was carried out on an Instron testing machine at a 5 mm/min crosshead speed. The Knoop hardness test was used to compare microhardness values. Data were analyzed using ANOVA, followed by REGWQ. Results: The group results, standard deviations, and statistical differences (p < 0.01) for Deflex, SR-Ivocap, and Meliodent were (A) flexural strength (MPa: 78.3 ± 1.0, a 69.8 ± 1.4, b 81.1 ± 1 a), (B) flexural modulus (GPa: 0.70 ± 0.13, a 0.85 ± 0.27, a 1.70 ± 0.23 b), (C) Knoop Hardness (kg/cm 2: 7.5 ± 1.0, a 13.5 ± 1.4, b 16.9 ± 1.0 c). Different superscript letters indicate significant difference. All Meliodent specimens fractured during flexural testing, but no Deflex specimens did. Conclusions: While polyamide denture material produced good fracture resistance, its modulus is not yet sufficiently high to be equal to standard PMMA materials. Clinical Implications. Polyamide has some attractive advantages, but will require modification to produce consistently better properties than current PMMA materials. © 2012 by the American College of Prosthodontists