High efficiency infrared antireflection coatings (ARCs) for space optics

Simple ARC designs for germanium (Ge) optics useful in spaceborne electro-optical systems have been generated. It is seen that the designs which are non-quarterwave in nature are efficient in terms of spectral coverage and residual reflection loss. They have been realised experimentally and the resulting ARCs are found to have very good spectral and durability properties.

Interaction between the Z-type DNA duplex and 1,3-propanediamine:crystal structure of d(CACGTG)(2) at 1.2 angstrom resolution

The crystal structure of a hexamer duplex d(CACGTG)(2) has been determined and refined to an R-factor of 18.3% using X-ray data up to 1.2 angstrom resolution. The sequence crystallizes as a left-handed Z-form double helix with Watson-Crick base pairing. There is one hexamer duplex, a spermine molecule, 71 water molecules, and an unexpected diamine (Z-5, 1,3-propanediamine, C3H10N2)) in the asymmetric unit. This is the high-resolution non-disordered structure of a Z-DNA hexamer containing two AT base pairs in the interior of a duplex with no modifications such as bromination or methylation on cytosine bases. This structure does not possess multivalent cations such as cobalt hexaammine that are known to stabilize Z-DNA. The overall duplex structure and its crystal interactions are similar to those of the pure-spermine form of the d(CGCGCG)(2) structure. The spine of hydration in the minor groove is intact except in the vicinity of the T5A8 base pair. The binding of the Z-5 molecule in the minor grove of the d(CACGTG)(2) duplex appears to have a profound effect in conferring stability to a Z-DNA conformation via electrostatic complementarity and hydrogen bonding interactions. The successive base stacking geometry in d(CACGTG)(2) is similar to the corresponding steps in d(CG)(3). These results suggest that specific polyamines such as Z-5 could serve as powerful inducers of Z-type conformation in unmodified DNA sequences with AT base pairs. This structure provides a molecular basis for stabilizing AT base pairs incorporated into an alternating d(CG) sequence.

Museoesineitä Itä-Karjalasta : Väinö Tuomaalan jatkosodan aikana keräämä esinekokoelma ja sen syntyhistoria

Jatkosodan aikana kerättiin Suomen valtaamalta alueelta Itä-Karjalasta tuhansittain museoesineitä Suomen museoihin. Kansallismuseon kokoelmiin kerättiin esineitä lähinnä suomenheimoisilta mutta myös isovenäläisiltä. Tämän tutkimuksen kohteena on lähes 400:n esineen kokoelma, joka toimitettiin Kansallismuseoon vuosina 1941 1944 ja merkittiin kansallisuudeltaan venäläiseksi. Näistä venäläisistä esineistä suurimman osan keräsi alikersanttina palvellut Väinö Tuomaala. Tutkimukseni tarkastelee Väinö Tuomaalan kokoelmaa ja etsii syitä siihen, miksi kokoelma on sellainen kuin se on, miksi se ja koko venäläisten esineiden kokoelma syntyi ja mitkä seikat vaikuttivat Tuomaalan esinevalintoihin. Tutkimuksen teoria rakentuu museologisen kirjallisuuden varaan. Tutkimuksessa tarkastellaan Väinö Tuomaalan kokoelman keräyskonteksteja. Keräyskonteksteihin kuuluvat kokoelman kerääjä, keräysajankohta ja -paikka sekä yhteenkuuluvat esineet, eli muut venäläiset esineet. Kerääjän tarkastelussa huomioidaan hänen henkilöhistoriansa ja etsitään mahdollisia keruuseen vaikuttaneita tekijöitä. Keräysajankohdan tarkastelussa huomio kiinnittyy keruuympäristöön, eli vallitseviin olosuhteisiin ja aatteelliseen ilmapiiriin, joiden vaikutuksen alaisena keruu suoritettiin. Primääriaineisto koostuu Kansallismuseon alaisen Kulttuurien museon yleisetnografisten esineiden kokoelmaan kuuluvista 198:sta Väinö Tuomaalan keräämästä esineestä verifikaatteineen, jotka ovat osa 393 esinettä käsittävästä venäläisestä kokoelmasta. Aineisto sisältää myös eri arkistojen materiaalia. Kansallisarkiston Sörnäisten toimipisteestä, entisestä sota-arkistota, löytyneitä sotapäiväkirjoja ja Tuomaalan kantakorttia on tutkimuksessa käytetty jatkosodan tapahtumien esittämiseen. Museoviraston hallinto-osaston arkiston kirjeet ja pöytäkirjat ovat antaneet tietoa kulttuurikeruun organisoinnista. Väinö Tuomaalan arkistokokoelma Seinäjoella sisältää Tuomaalan keräämää perinneaineistoa, hänen puheitaan, lehtikirjoituksiaan ja kirjeenvaihtoaan. Myös Evijärven kunnantalon kotiseutuarkistosta löytyneet kirjeet ovat valottaneet Tuomaalan jatkosodan aikaista keruutoimintaa. Suomalaisen Kirjallisuuden Seuran arkistot ovat tarjonneet materiaalia jatkosodan aikaisesta kulttuurikeruusta. Koko venäläisten esineiden kokoelma syntyi sattumalta ja organisoimattoman toiminnan tuloksena, jossa aktiivisia toimijoita olivat yksittäiset kerääjät. Intohimoisesta suhtautumisesta kansatieteellistä keruuta kohtaan johtuen, Tuomaala olisi todenäköisesti kerännyt museoesineitä missä päin Itä-Karjalaa tahansa. Väinö Tuomaalan Itä-Karjalassa keräämä esinekokoelma oli luonnollinen jatke hänen kotiseudullaan aloittamalleen keräystoiminnalle. Tuomaalan jatkosodan aikana keräämä kokoelma on kerääjän mieltymysten mukainen yritys kerätä vanhaa itäkarjalaista, kansallista talonpoikaiskulttuuria. Tuomaala pyrki keräämään klassista kansatieteellistä aineistoa monipuolisesti kansankulttuurin eri elämänalueilta. Tuomaalan esinekeruussa näkyi vahvasti talonpoikaiskulttuurin ihannointi ja halu pelastaa osa siitä tuleville sukupolville. Yrityksen onnistumiseen vaikuttivat sodanajan olosuhteet sekä aatteellinen ilmapiiri. Esineiden saatavuudella oli merkittävä osa kokoelman muodostumiseen, samoin Tuomaalan käsityksillä heimokansoista, Suur-Suomesta ja venäläisistä. Keruuvalintoihin ja keruun jatkumiseen vaikuttivat myös Kansallismuseon henkilökunta ja työstä saatu tunnustus.

Liquid Limit Of Kaolinitic Soils

This paper elucidates the relative importance of soil structure and various compositional factors in influencing the liquid limit of natural kaolinitic soils. Earlier studies dealt with purified systems and anticipated that the liquid limit of the soils would increase with percentage clay size fraction and surface area, and that soils with a greater degree of paricle flocculation would possess a higher liquid limit than soils with a more parallel particle arrangement. The results revealed that the inter-particle attraction and repulsion forces have a prominent role in determining the liquid limit of kaolinitic soils. These forces determine the particle arrangement (clay fabric) which in turn regulates the liquid limit values. The influence of clay fabric was ascertained from the relationships of liquid limit with shrinkage limit and sediment volume (in water) values. It was anticipated that kaolinitic soils with a greater degree of particle flocculatin and a higher liquid limit would shrink less and occupy a higher sedimentation volume. As expected an increase in liquid limit was accompanied by an increase in shrinkage limit and sediment volume in water.

A novel supersecondary structure in globular proteins comprising the collagen-like helix and ?-turn

A structure consisting of the polyproline-II or collagen-like helix immediately succeeded by a ?-turn is seen in several synthetic peptides and has been suggested to be the conformational requirement for proline hydroxylation in nascent procollagen. Using a simple algorithm for detecting secondary structures, we have analysed crystal structure data on 40 globular proteins and have found eight examples of the collagen-helix + ?-turn supersecondary structure in 15 proteins that contain the collagen-like helical segments.

Electrical switching in benzidine-DDQ under pressure

The effect of pressure on non-ohmic conduction and electrical switching in the charge transfer complex benzidine-DDQ has been studied up to a pressure of 7·66 GPa at a temperature of 300K. Pulsed I-V measurements reveal heating contribution to non-ohmicity and switching. At high electric fields (∼ 3 × 103 V/cm), the sample switches from high resistance OFF state of several kiloohms to low resistance ON state of several ohms. Temperature dependence of conductivity of ON state show semiconducting behaviour with very low activation energy.

Studies on the biosynthesis of cytochrome P-450 in rat liver—A probe with phenobarbital

Cytochrome P-450 has been purified from phenobarbital-treated rat livers to a specific content of 17 nmol/mg protein. The major species purified has a molecular weight of 48,000. Using the purified antibody for the cytochrome P-450 preparation it has been shown that the major product synthesized in vivo and in the homologous cell-free system in vitro is the 48,000 molecular weight species. Poly(A)-containing RNA isolated from phenobarbital-treated animals codes for the synthesis of the 48,000 molecular weight species in the wheat germ and reticulocyte lysate cell-free systems. It is concluded that cytochrome P-450 synthesis does not involve processing of a polyprotein precursor, although certain minor modifications including glycosylation of the primary translation product are not ruled out. Phenobarbital treatment of the animal results in a significant increase in the cytochrome P-450 messenger activity as measured in the wheat germ cell-free system.

Studies on nucleotidases in plants: Fluorescence and kinetic properties of nucleotide pyrophosphatase from mung bean (Phaseolus aureus) seedlings

Nucleotide pyrophosphatase of mung bean seedlings has earlier been isolated in our laboratory in a dimeric form (Mr 65,000) and has been shown to be converted to a tetramer by AMP and to a monomer by p-hydroxymercuribenzoate. All the molecular forms were enzymatically active with different kinetic properties. By a modified procedure using blue-Sepharose affinity chromatography, we have now obtained a dimeric form of the enzyme which is desensitized to AMP interaction. The molecular weight of the desensitized form of the enzyme was found to be the same as that of the native dimeric enzyme. However, the desensitized enzyme functioned with a linear time course, contrary to the biphasic time course exhibited by the native enzyme. In addition, it was not converted to a tetramer on the addition of AMP, had only one binding site for adenine nucleotides, and p-hydroxy-mercuribenzoate had no effect on the time course of the reaction or on the molecular weight of the enzyme. The temperature optimum of the desensitized enzyme was found to be 67 °C in contrast to the optimum of 49 °C for the native dimer. Fifty percent of the tryptophan residues of the desensitized enzyme were not accessible for quenching by iodide. Fluorescence studies gave Kd values of 0.34, 2.2, and 0.8 mImage for AMP, ADP, and ATP, which were close to the Ki values of 0.12, 2.2, and 0.9 mImage , respectively, for these nucleotides. The binding and inhibition studies with AMP and its analogs showed that the 6-amino group and the 5′-phosphate group were essential for the inhibition of the enzyme activity.

Psi-angle dependence of geminal proton–carbonyl-13C coupling constants in peptides. A theoretical investigation†

Theoretical calculations of the geminal carbonyl-13C- proton coupling constant, 2J(C′H), in α-amino acids have been carried out using Dirac Vector model and Penney-Dirac bond order formulations. The results indicate that the couplings are dependent on the backbone torsion angle psi (ψ) of the amino acid residues in peptides. The meagre available experimental data seem to support the theoretical findings.

Compensator for constant relative stability in process control systems

Process control systems are designed for a closed-loop peak magnitude of 2dB, which corresponds to a damping coefficient () of 0.5 approximately. With this specified constraint, the designer should choose and/or design the loop components to maintain a constant relative stability. However, the manipulative variable in almost all chemical processes will be the flow rate of a process stream. Since the gains and the time constants of the process will be functions of the manipulative variable, a constant relative stability cannot be maintained. Up to now, this problem has been overcome either by selecting proper control valve flow characteristics or by gain scheduling of controller parameters. Nevertheless, if a wrong control valve selection is made then one has to account for huge loss in controllability or eventually it may lead to an unstable control system. To overcome these problems, a compensator device that can bring back the relative stability of the control system was proposed. This compensator is similar to a dynamic nonlinear controller that has both online and offline information on several factors related to the control system. The design and analysis of the proposed compensator is discussed in this article. Finally, the performance of the compensator is validated by applying it to a two-tank blending process. It has been observed that by using a compensator in the process control system, the relative stability could be brought back to a great extent despite the effects of changes in manipulative flow rate.

Interactions of tris buffer with nucleotides: the crystal structure of tris(hydroxymethyl)methylammonium adenosine 5'-diphosphate dihydrate

The crystal and molecular structures of the Tris salt of adenosine 5'-diphosphate were determined from X-ray diffraction data. The crystals are monoclinic, space P21, and Z = 2 with a=9.198 (2) A, b=6.894 (1) A, c=18.440 (4) A, and beta = 92.55 (2) degrees. Intensity data were collected on an automated diffractometer. The structure was solved by the heavy-atom technique and refined by least squares to R = 0.047. The ADP molecule adopts a folded conformation. The conformation about the glycosidic bond is anti. The conformation of the ribose ring is close to a perfect C(2')-endo-C-(3')-exo puckering. The conformation about C(4')-C(5') is gauche-gauche, similar to other nucleotide structures. The pyrophosphate chain displays a nearly eclipsed geometry when viewed down the P-P vector, unlike the staggered conformation observed in crystal structures of other pyrophosphates. The less favorable eclipsed conformation probably results from the observed association of Tris molecules with the polar diphosphate chain through electrostatic interactions and hydrogen bonds. Such interactions may play an important role in Tris-buffered aqueous solutions of nucleotides and metal ions.

Dynamics of charge transfer in the excited amine complexes of the fullerenes C60 and C70.: A picosecond laser flash photolysis study

In benzene solution, C60 and C70 interact weakly in the ground state with amines having favourable oxidation potentials. Picosecond time-resolved absorption measurements show that on photoexcilation, the weak complexes undergo charge separation to produce ion pairs which in turn undergo fast geminate recombination either to produce the triplet state of the fullerenes or give back the ground slate of the complex, depending on the oxidation potential of the amine. Free-ion yield is generally negligible.

Conformational Polymorphism in Telomeric Structures: Loop Orientation and Interloop Pairing in d(G4TnG4),

Sequence repeats constituting the telomeric regions of chromosomes are known to adopt a variety of unusual structures, consisting of a G tetraplex stem and short stretches of thymines or thymines and adenines forming loops over the stem. Detailed model building and molecular mechanics studies have been carried out for these telomeric sequences to elucidate different types of loop orientations and possible conformations of thymines in the loop. The model building studies indicate that a minimum of two thymines have to be interspersed between guanine stretches to form folded-back structures with loops across adjacent strands in a G tetraplex (both over the small as well as large groove), while the minimum number of thymines required to build a loop across the diagonal strands in a G tetraplex is three. For two repeat sequences, these hairpins, resulting from different types of folding, can dimerize in three distinct ways-i.e., with loops across adjacent strands and on same side, with loops across adjacent strands and on opposite sides, and with loops across diagonal strands and on opposite sides-to form hairpin dimer structures. Energy minimization studies indicate that all possible hairpin dimers have very similar total energy values, though different structures are stabilized by different types of interactions. When the two loops are on the same side, in the hairpin dimer structures of d(G(4)T(n)G(4)), the thymines form favorably stacked tetrads in the loop region and there is interloop hydrogen bonding involving two hydrogen bonds for each thymine-thymine pair. Our molecular mechanics calculations on various folded-back as well as parallel tetraplex structures of these telomeric sequences provide a theoretical rationale for the experimentally observed feature that the presence of intervening thymine stretches stabilizes folded-back structures, while isolated stretches of guanines adopt a parallel tetraplex structure