Structures, Phase Transitions and Tricritical Behavior of the Hybrid Perovskite Methyl Ammonium Lead Iodide.

We have examined the crystal structures and structural phase transitions of the deuterated, partially deuterated and hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI3) using time-of-flight neutron and synchrotron X-ray powder diffraction. Near 330 K the high temperature cubic phases transformed to a body-centered tetragonal phase. The variation of the order parameter Q for this transition scaled with temperature T as Q ∼ (Tc-T)ß, where Tc is the critical temperature and the exponent ß was close to », as predicted for a tricritical phase transition. However, we also observed coexistence of the cubic and tetragonal phases over a range of temperature in all cases, demonstrating that the phase transition was in fact first-order, although still very close to tricritical. Upon cooling further, all the tetragonal phases transformed into a low temperature orthorhombic phase around 160 K, again via a first-order phase transition. Based upon these results, we discuss the impact of the structural phase transitions upon photovoltaic performance of MAPbI3 based solar cells.

The Kinetic Significance of V5 in n-Butane Oxidation Catalyzed by Vanadium Phosphates

Maleic anhydride, a precursor to polyester resins, is made by oxidation of n-butane over vanadium phosphate catalysts. This system is of general interest because it is the only heterogeneously catalyzed, alkane-selective oxidation reaction in commercial use. Time-resolved in situ x-ray absorption spectroscopy shows that when either alphaI-VOPO4/SiO2 or (VO)2P2O7/SiO2 catalysts are exposed to n-butane, the rate of maleic anhydride formation is proportional to the rate of decay of V5+ species in the catalyst. Thus V5+ species are kinetically significant for the production of maleic anhydride and not just for the production of by-products. The results also suggest that V5+ species may play a role in the initial hydrogen abstraction from n-butane, the rate-determining step in the reaction sequence. V4+ sites appear to be responsible for by-product formation.

X-Ray Photoconductive Nanocomposites

The successful development of digital radiography depends, to a large extent, on the availability of suitable x-ray photoconductors. The x-ray photoconductive nanocomposites reported here combine the advantages of both inorganic and organic compounds. An inorganic compound was finely dispersed in an organic polymer. The inorganic compound, with its large x-ray absorption efficiency, functioned as the x-ray absorber, and the polymer provided good dielectric properties and ease of thin-film preparation. The preparation procedures and the x-ray photoconductive properties of a specific example, a 50 percent by weight nanocomposite of bismuth triiodide and nylon-11, are discussed in detail.

Modular methodology for determination of polychlorinated biphenyls in soil as Aroclors and individual congeners.

A comprehensive screening and confirmatory method was developed for monitoring polychlorinated biphenyls (PCBs), both as Aroclors and as individual congeners. This approach incorporates extraction, extract cleanup, and analysis modules designed to match cost, time, and data quality requirements. Soxhlet, sonication, supercritical fluid, and accelerated solvent extractions were evaluated. Carbon chromatographic cleanup procedures were used for separation of congeners on the basis of ortho substitutions, which permitted calculation of toxicity equivalents. Individual congener determinations, congener total histograms, and peak comparison techniques for Aroclor identification were elaborated by using high and low resolution mass spectrometric data. A screening procedure based on immunoassay using the Ohmicron PCB RaPID Assay kit gave results comparable to those obtained by gas chromatography with electron capture detection in the range 0.40-230 ppm, when the appropriate Aroclor calibrator was used.

Software-based mass spectral enhancement to remove interferences from spectra of unknowns.

Gas chromatography-mass spectrometry data from the analysis of complex environmental samples were converted into ASCII text and imported into a personal computer spreadsheet. A macro was written to perform mass spectral enhancement by statistical and mathematical procedures to separate the spectra of compounds of interest from interfering mass spectral responses, such as those of broadly eluting hydrocarbons. The extracted mass spectra were compared to reference spectra, with the result that usually 80-90% of the ions common to those in the reference spectra were successfully extracted by using this method. This procedure improved mass spectral quality and the ability of the data system to perform successful library searches. The fitted quality parameters showed systematic improvements after the data were subjected to the spectral enhancement procedures. These procedures could help to identify unknowns by separating their spectra from other signals, such as those of background aliphatic hydrocarbons.

Trauma and the development of borderline personality disorder.

Prolonged and severe trauma, particularly trauma that occurs early in the life cycle, tends to result in a chronic inability to modulate emotions. When this occurs, people can mobilize a range of behaviors that are best understood as attempts at self-soothing. Some of these attempts include clinging and indiscriminate relationships with others in which old traumas are re-enacted over time, as well as more self-directed behaviors such as self-mutilation, eating disorders, and substance abuse. Usually, these behaviors will coexist. Patients with complicated trauma histories often repetitively attempt suicide or engage in chronic self-destructive behavior, and need to address issues of childhood trauma, neglect, and abandonment, both in the past and as re-experienced in current relationships. When treating these patients, therapists must anticipate that painful affects related to interpersonal safety, anger, and emotional needs may give rise to dissociative episodes, which may, in turn, be accompanied by increased self-destructive behavior. The therapy must clarify how current stresses are experienced as a return of past traumas and how small disruptions in present relationships are seen as a repetition of prior abandonment. As part of this, it is essential that the therapist provide validation and support, and avoid participating in a re-enactment of the trauma. Fear needs to be tamed in order for people to be able to think and be conscious of current needs. This bodily response of fear can be mitigated by safety of attachments, security of meaning schemes, and by a body whose reactions to environmental stress can be predicted and controlled. One of the great mysteries of the processing of traumatic experience is that as long as the trauma is experienced as speechless terror, the body continues to keep score and react to conditioned stimuli as a return of the trauma. When the mind is able to create symbolic representations of these past experiences, however, there often seems to be a taming of terror, a desomatization of experience. As Ducey and van der Kolk found in the Rorschachs of Vietnam veterans, patients were unresponsive to outside influences (good or bad) as long as they remained in a state of psychic numbing. Faced with intrusions of past trauma in their current emotional life, patients' initial sense of being overwhelmed was mastered only when a link between past trauma and current perceptions became understood.(ABSTRACT TRUNCATED AT 400 WORDS)

The history of trauma in psychiatry.

The accidental separation of PTSD and the dissociative disorders, based on the unfortunate fact that the PTSD and the dissociative disorder workgroups of the DSM-III never met to compare data, and the lack of knowledge within the workgroups of existing research connecting these disorders, will continue in the DSM-IV. That separation, however, is slowly being eroded by a solid body of research that shows that these conditions rarely occur independently. Thus, contemporary research is beginning to show that the original concept of "hysteria," formulated 150 years ago to capture a group of patients who have complex psychological and somatic problems and whose problems often elude intervention from the medical and psychological professions, is alive and well among patients on the verge of the twenty-first century. Although the DSM process has attempted to create cleaner diagnostic categories, 100 years of research on traumatized patients consistently shows that these patients defy easy classification, and that they seem to have symptoms that represent somatic, social, symbolic, and intrapsychic adaptations to having experienced overwhelming terror. Thus, what the DSM split when it abolished hysteria as a diagnosis, has once again been found to constitute a syndrome, a conglomeration of symptoms, first defined by Briquet and Janet more than 100 years ago, which is the result of severe and prolonged interpersonal abuse, usually starting in childhood. One hundred years of research has shown us that patients often cannot remember and, instead, re-enact their dramas. The professions ministering to these patients have had similar problems with remembering the past, and thrice in this century have forgotten the hard-earned lessons from our patients. It is not likely that these amnesias and dissociations will be a thing of the past; they are likely to continue as long as physicians and psychologists are faced, helplessly, with man's inhumanity to man.

Production of perfluoroalkylated nanospheres from buckminsterfullerene.

Perfluoroalkylated nanospheres have been prepared by reaction of fullerenes with a variety of fluoroalkyl radicals. The latter are generated by thermal or photochemical decomposition of fluoroalkyl iodides or fluorodiacyl peroxides. Up to 16 radicals add to C(60) to afford easily isolable fluoroalkylated derivatives. The monosubstituted radical adducts were detected by electron spin resonance in the early stages of the fluoroalkylation reactions. These spheroidal molecules are thermally quite stable, soluble in fluoroorganic solvents, chemically resistant to corrosive aqueous solutions, and more volatile than the parent fullerenes. Films of the sublimed material display properties typical for a perfluoroalkylated material.

Crystal Structure and Optical Properties of Cd32S14(SC6H5)36. DMF4, a Cluster with a 15 Angstrom CdS Core.

Recrystallization of the solid Cd(10)S(4)(SC(6)H(5))(12) from a solution of pyridine and N, N-di-methylformamide (DMF) results in the formation of the cluster Cd(32)S(14)(SC(6)H(5))(36)-DMF(4) as pale yellow cubes. The structure consists of an 82-atom CdS core that is a roughly spherical piece of the cubic sphalerite lattice approximately 12 angstroms in diameter. The four corners of the lattice are capped by hexagonal wurtzite-like CdS units, which results in an overall tetrahedral cluster approximately 15 angstroms in diameter. This cluster dissolves intact in tetrahydrofuran where its absorption spectrum reveals a sharp peak at 358 nanometers at room temperature and its emission spectra show a strong broad band at 500 nanometers.

Synthesis and Single-Crystal X-ray Structure of a Highly Symmetrical C60 Derivative, C60Br24.

C(60) and liquid bromine react to form C(60)Br(24), a crystalline compound isolated as a bromine solvate, C(60)Br(24)(Br(2))(x), The x-ray crystal structure defines a new pattern of addition to the carbon skeleton that imparts a rare high symmetry. The parent C(60) framework is recognizable in C(60)Br(24), but sp(3) carbons at sites of bromination distort the surface, affecting conformations of all of the hexagonal and pentagonal rings. Twenty-four bromine atoms envelop the carbon core, shielding the 18 remaining double bonds from addition. At 150 degrees to 200 degrees C there is effectively quantitative reversion of C(60)Br(24) to C(60) and Br(2).