DIP angle dependence on track formation sensitivity in antioxidant doped CR-39 plates

Recently, space radiation dosimetry measurements were made by passive and active detectors inside the Spacelab [STS-47 (FMPT): 300km, 57°, STS-65 (IML-2 mission): 300km, 28.5°]. The LET distributions obtained by antioxidant doped CR-39 inside the Spacelab were compared with those measured by the tissue equivalent proportional counter (TEPC) and the real time radiation monitoring device (RRMD) consisting of eight silicon detectors. While both distributions by CR-39 are in good agreement with those obtained by active detectors over the region of LET of several tens to 200 keV/μm, a significant difference in the LET region of smaller than several tens keV/μm is seen. It is considered to be caused by the dip angle dependence of track formation sensitivity in CR-39. The track formation sensitivity for different dip angle were measured for several high heavy energy ions. Using these results, the correction for the dip angle was made for the LET distribution. The corrected result is consistent with the results obtained by active detectors.     

Efficient, enantioselective assembly of silanediol protease inhibitors

A five-step assembly of silicon-protected dipeptide mimics from commercially available reagents is described. This methodology makes silanediol protease inhibitors readily available for the first time. The sequence features asymmetric hydrosilylation, a novel reduction of a silyl ether to a silyllithium reagent, and addition of this dianion to a sulfinimine, to produce the complete inhibitor skeleton with full control of stereochemistry. Oxidation of the primary alcohol to an acid completes the synthesis.     

New limit on the lepton-flavor-violating decay μ+→e+γ

We present a new result based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institut in 2009 and 2010, in search of the lepton-flavor-violating decay μ(+)e(+)γ. The likelihood analysis of the combined data sample, which corresponds to a total of 1.8×10(14) muon decays, gives a 90% C.L. upper limit of 2.4×10(-12) on the branching ratio of the μ(+)→e(+)γ decay, constituting the most stringent limit on the existence of this decay to date.     

Dose equivalents inside the MIR Space Station measured by the combination of CR-39 plates and TLDs and their comparison with those on Space Shuttle STS-79, -84 and -91 missions

In 1997, four dosimeter packages, each of which contains two CR-39 plates and 18 TLDs (Mg2SiO4:Tb), were placed inside the MIR Space Station and flew on an orbit with an inclination angle of 51.6 degrees and an altitude of approximately 400 km for 40 days. We estimated the absorbed doses, dose equivalents and effective quality factors during the flight by combining CR-39 data and TLD data. We then compared these results to those obtained with the same analysis method from the dosimeter packages on board Space Shuttle missions STS-79, -84 and -91 that flew along the same orbit. Finally, the differences between our results and those obtained by another group using passive dosimeters on the MIR are discussed.     

Design,Synthesis, and Characterization of Quinoxaline Derivatives as a Potent Antimicrobial Agent

A series of quinoxalinone derivatives were synthesized by the reaction of o‐phenylenediamine with oxalic acid to yield 1, 4‐dihydro quinoxaline‐2, 3‐dione ( 1 ) and then treated with thionyl chloride to yield 2, 3 dichloro quinoxaline ( 2 ). This was further reacted with hydrazine hydrate to produce 2, 3‐dihydrazinyl quinoxaline ( 3 ). This was finally reacted with substituted aromatic aldehydes to produce 2,3‐bis[2‐(sustituted benzylidine) hydrazinyl] quinoxalines ( 4 ). These quinoxalinone derivatives were characterized by infrared spectroscopy and nuclear magnetic resonance spectroscopy and MASS spectral data. All the synthesized compounds were evaluated for their antimicrobial activity. The results of the antimicrobial study revealed that compounds 4c , 4d , and 4i were active and exhibited better inhibitory activities as compared to standard drug ciprofloxacin. The results were further checked with protein legend interaction by using docking studies, and all the compounds exhibited good docking scores between ?8.72 and ?11.29 kcal/mol against dihydrofolate reductase protein fragment from Staphylococcus aureus (PDB ID‐4XE6). Among all compound, 4c has shown maximum docking score and found in agreement to in vitro studies.     

SNAr reaction of 2,5‐dinitrofuran: A mild and efficient method for the preparation of 2‐aryloxy‐5‐nitrofuran

2,5‐Dinitrofuran which can be easily prepared by nitration of 2‐nitrofuran, on phase transfer catalysed S_NAr reaction with phenol gave good yield of 2‐aryloxy‐5‐nitrofuran. J. Heterocyclic Chem., (2011).     

Silver sequestration of halides for the activation of Pd(OAc)2 catalyzed Mizoroki‐Heck reaction of 1,1 and 1,2 ‐ Disubstituted alkenes

A ligand free catalytic system consisting of Pd(OAc)₂ (cat) and stoichiometric quantities of silver salts, AgOAc or AgBF₄, exhibit high efficiency in the Mizoroki‐Heck arylation, transforming aryl iodides and 1,1 as well as 1,2 disubstituted alkenes into 1,1,2 – trisubstituted aryl alkenes in excellent yields in very short reaction times.     

A cesium fluoride promoted efficient and rapid multicomponent synthesis of functionalized 2-amino-3-cyano-4H-pyran and spirooxindole derivatives

A rapid, one-pot and highly efficient protocol for the synthesis of pharmaceutically interesting functionalized 2-amino-3-cyano-4H-pyran and spirooxindole derivatives has been developed using commercially available Cs F as a catalyst in the reaction of malononitrile and aryl aldehydes or isatins with 1,3-cyclohexanediones. The major advantages of this methodology are excellent yield at ambient temperature, very short reaction time(5–10 min), and use of an inexpensive catalyst.     

Protein structure prediction aided by geometrical and probabilistic constraints

Database-assisted ab initio protein structure prediction methods have exhibited considerable promise in the recent past, with several implementations being successful in community-wide experiments (CASP). We have employed combinatorial optimization techniques toward solving the protein structure prediction problem. A Monte Carlo minimization algorithm has been employed on a constrained search space to identify minimum energy configurations. The search space is constrained by using radius of gyration cutoffs, the loop backbone dihedral probability distributions, and various secondary structure packing conformations. Simulations have been carried out on several sequences and 1000 conformations have been initially generated. Of these, 50 best candidates have then been selected as probable conformations. The search for the optimum has been simplified by incorporating various geometrical constraints on secondary structural elements using distance restraint potential functions. The advantages of the reported methodology are its simplicity, and modifiability to include other geometric and probabilistic restraints.     

Monitoring the formation of self-assembled monolayers of alkanedithiols using a micromechanical cantilever sensor

Using a micromechanical cantilever device, the surface stress induced during the growth of alkanedithiol (HS(CH2)nSH) monolayers on gold in solution is continuously monitored and reported. Adsorption of alkanedithiols of varying chain lengths is observed and compared to each other, as well as to the adsorption of hydroxyalkanethiols (HS(CH2)nOH) and alkanethiols (HS(CH2)nCH3). The results have revealed a significant change in surface stress on the basis of the chain length of the alkanedithiol. The long-chain (n > 10) alkanedithiol adsorption imposes a tensile stress on the gold-coated surface of the cantilever rather than the compressive stress exhibited by both alkanethiols and short-chain dithiols. Our results suggest a phenomenon in which the two thiols of the alkanedithiol adsorb onto the gold surface forming a loop inducing a tensile stress on the cantilever for long chain lengths. This study shows that micromechanical cantilever sensors can be very valuable tools in the exploration and characterization of self-assembled monolayers.