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Conformer-specific dynamics Conformation-dependent dynamics play an important role in organic chemistry syntheses such as electrocyclic reactions, as well as in biological processes such as protein folding. However, current time-resolved experimental methods struggle to distinguish conformers from each other, and conformational isomerism is usually analyzed through reactant and product distributions. Using a combination of mega–electron volt ultrafast electron diffraction and quantum wave packet simulations, Champenois et al . directly followed the photochemical electrocyclic ring opening of the molecule α-phellandrene with femtosecond time resolution and confirmed that the transformation of a specific molecular conformer follows the famous Woodward-Hoffmann rules. The proposed method is potentially a powerful tool to follow conformer specificity in various organic and biological systems in real time. —YS

Many important biological and chemical processes are initiated by the transfer of a proton from a donor to an acceptor group within a molecule and are regulated by the interplay of nuclear and electronic dynamics. The electronic dynamics of proton transfer are well-studied, yet the nuclear dynamics have never been spatiotemporally resolved. Herein, we present a direct observation of the nuclear motions leading to and ensuing from photochemical proton transfer in o-nitrophenol using ultrafast electron diffraction. The proton transfer step is identified by the transient compression of the donor-acceptor distance and captured on the femtosecond timescale with sub-Angstrom resolution. Supported by ab initio multiple spawning simulations, our observations uncover the structural changes mediating excited-state relaxation. Our work provides an unprecedented mechanistic insight into the photochemical proton transfer mechanism and photo-relaxation dynamics of o-nitrophenol, unambiguously connecting an experimental observable to a process previously confined to theoretical models.

Across ten experiments, we investigated the role of attentional control in the allocation of visual short-term memory resources to relevant visual information when multiple feature dimensions were present. In each experiment, a change detection task was embedded within a task switching paradigm wherein the relevant feature dimension on which to detect changes could either repeat (e.g., colour-colour) or switch (e.g., colour-orientation) on a given trial. Results show a consistent impact of dimension switching across a range of measures and experimental manipulations (e.g., set size, feature overlap). Our findings suggest that these dimension switch costs originate from an origin distinct to that observed with typical task switching costs. Manipulations of cue-stimulus (Experiment 3a) and response-cue (Experiment 3b) intervals—which are associated with moderation of the magnitude of task switch costs—had no influence on dimension switch costs, and cue switches—associated with priming accounts of task switch costs—did not contribute to the dimension switch cost to any great extent (Experiment 4). We discuss the results in relation to theoretical models of visual short-term memory in terms of the impact of dimension switching on efficient resource allocation.

Electronic and nuclear dynamics in one Because of the complex, ultrafast interplay between nuclear and electronic degrees of freedom, probing both nuclear and electronic dynamics in excited electronic states within a single time-resolved experiment is a great challenge. Yang et al. used ultrafast electron diffraction in combination with ab initio nonadiabatic molecular dynamics and diffraction simulations to study the relaxation dynamics of isolated pyridine molecules after photoexcitation to the S 1 state (see the Perspective by Domcke and Sobolewski). They showed that electronic state evolution and molecular structural changes can be recorded simultaneously and independently by tracing a transient signal in small-angle inelastic scattering and large-angle elastic diffraction, respectively. Science , this issue p. 885 ; see also p. 820

We investigated the ultrafast photochemical ring-opening in the molecule α-phellandrene by a combination of megaelecronvolt ultrafast electron diffraction and excited state ab initio multiple spawning wavepacket simulations. α- Phellandrene exhibits a number of different conformers which produce different ring-opening photoproducts according to the Woodward-Hoffmann rules. In our study we image the conversion of a specific conformer of α-phellandrene in the Woodward-Hoffmann predicted photoproduct in real time and space.

Pump-probe measurements aim to capture the motion of electrons and nuclei on their natural timescales (femtoseconds to attoseconds) as chemical and physical transformations take place, effectively making “molecular movies” with short light pulses. However, the quantum dynamics of interest are filtered by the coordinate-dependent matrix elements of the chosen experimental observable. Thus, it is only through a combination of experimental measurements and theoretical calculations that one can gain insight into the internal dynamics. Here, we report on a combination of structural (relativistic ultrafast electron diffraction, or UED) and spectroscopic (time-resolved photoelectron spectroscopy, or TRPES) measurements to follow the coupled electronic and nuclear dynamics involved in the internal conversion and photodissociation of the polyatomic molecule, diiodomethane (CH_{2}I_{2}). While UED directly probes the 3D nuclear dynamics, TRPES only serves as an indirect probe of nuclear dynamics via Franck-Condon factors, but it is sensitive to electronic energies and configurations, via Koopmans’ correlations and photoelectron angular distributions. These two measurements are interpreted with trajectory surface hopping calculations, which are capable of simulating the observables for both measurements from the same dynamics calculations. The measurements highlight the nonlocal dynamics captured by different groups of trajectories in the calculations. For the first time, both UED and TRPES are combined with theory capable of calculating the observables in both cases, yielding a direct view of the structural and nonadiabatic dynamics involved.

The development of ultrafast gas electron diffraction with nonrelativistic electrons has enabled the determination of molecular structures with atomic spatial resolution. It has, however, been challenging to break the picosecond temporal resolution barrier and achieve the goal that has long been envisioned—making space- and-time resolved molecular movies of chemical reaction in the gas-phase. Recently, an ultrafast electron diffraction (UED) apparatus using mega-electron-volt (MeV) electrons was developed at the SLAC National Accelerator Laboratory for imaging ultrafast structural dynamics of molecules in the gas phase. The SLAC gas-phase MeV UED has achieved 65 fs root mean square temporal resolution, 0.63 A spatial resolution, and 0.22 A−1 reciprocal-space resolution. Such high spatial-temporal resolution has enabled the capturing of real-time molecular movies of fundamental photochemical mechanisms, such as chemical bond breaking, ring opening, and a nuclear wave packet crossing a conical intersection. In this paper, the design that enables the high spatial-temporal resolution of the SLAC gas phase MeV UED is presented. The compact design of the differential pump section of the SLAC gas phase MeV UED realized five orders-of-magnitude vacuum isolation between the electron source and gas sample chamber. The spatial resolution, temporal resolution, and long-term stability of the apparatus are systematically characterized.

Settlement and growth of quagga mussels Dreissena rostriformis bugensis were monitored in Lake Mead, NV, USA, where the first dreissenid occurrence was confirmed in the western United States. To measure the settlement rate of these invasive mussels, seven acrylonitrile butadiene styrene (ABS) pipes were attached to a line in shallow water (7.7 m below the surface) since November 23, 2007; eight ABS pipes were placed on another line in deep water (13.4 m below the surface) since January 3, 2008. Quagga mussels were sampled from these pipes on March 19, May 21, July 9, October 20, and December 19, 2008. Active settlement of veligers was recorded in all sampling events. The settlement rates of quagga mussels did not differ among the two lines and the highest settlement rate was found from October 20 to December 19. Three methods were used to estimate the growth of quagga mussels in Lake Mead: caged mussels, size distribution analyses on both natural populations and mussels attached to ABS pipes. Caged mussels were held in Las Vegas Boat Harbor from July 31, 2007 to March 19, 2008, where smaller mussels grew faster than larger ones. Size distribution data on two natural populations of quagga mussels collected from Sentinel Island and Indian Canyon in 2007 also showed that the growth rates decreased significantly as mussel size increased. Shell length data of cohorts collected from the ABS pipes were also used to estimate the growth of quagga mussels. The growth patterns of quagga mussels from the two lines were quite similar with the lowest growth rates detected from late summer to early autumn. The information on settlement and growth of quagga mussels from this study can help understand their population dynamics in the western United States.

SummaryRemission is a new research outcome indicating long-term wellness. Remission not only sets a standard for minimal severity of symptoms and signs (resolution); it also sets a standard for how long symptoms and signs need to remain at this minimal level (6 months). Individuals who achieve remission from schizophrenia have better subjective well-being and better functional outcomes than those who do not. Research suggests that remission can be achieved in 20–60% of people with schizophrenia. There is some evidence of the usefulness of remission as an outcome indicator for clinicians, service users and their carers. This article reviews the literature on remission in schizophrenia and asks whether it could be a useful clinical standard of well-being and a foundation for functional improvement and recovery.

We all desire the experience of happiness, but happiness is not an attainable goal in and of itself; it is a derivative, or after-effect, of something. The more we focus on our experience of happiness the less that it exists. A paradox arises. Happiness and well-being are experienced when individuals relinquish concerns about the self and focus on an entity outside of the self. Flow theory proposes that optimal experience is ascertained through an intense focus on an activity that contains clear goals, immediate feedback, and a balanced skill/challenge ratio. I propose that using the activity-specific model of flow in a broader, life plan view, context utilizes the paradox of happiness and provides a useful framework for happiness goal attainment.

The shared management of patients with schizophrenia in primary care can only succeed if underpinned by valid, easily administered and clinically relevant outcome measures. While conditions such as depression and anxiety lend themselves to this approach through the development, over a number of years, of patient- and observer-rated scales, schizophrenia still lacks the capacity for meaningful outcome measures. Recently, two international working groups have developed the concept of remission in schizophrenia and recommended a simple, brief and clinically valid measure based upon improvement in key symptoms over a specified time period. The authors consider this concept and its application to primary care both as a commissioning tool and to facilitate shared care of this chronic medical condition.

Context: Nonradiographic tests to identify fractures rely on a patient's report of increased pain at the site of injury. These tests can be misleading and produce false-positive or false-negative results because of differences in pain tolerance. A painless technique using a tuning fork and stethoscope to detect fractures has undergone limited review in the athletic training literature. Objective: To determine if the use of a 128-Hz vibrating tuning fork and stethoscope were effective in identifying fractures. Design: Cross-sectional study. Setting: University athletic training room or local orthopaedic center when fractures were suspected. Patients or Other Participants: A total of 37 patients (19 males, 18 females) volunteered. Main Outcome Measure(s): A diminished or absent sound arising from the injured bone as compared with the uninjured bone represented a positive sign for a fracture. Radiographs interpreted by the attending orthopaedic physician provided the standard for comparison of diagnostic findings. Results: Sensitivity was 0.83 (10∶12), specificity was 0.80 (20∶25), positive likelihood ratio was 4.2, negative likelihood ratio was 0.21, and diagnostic accuracy was 81% (30∶37). Conclusions: The tuning fork and stethoscope technique was an effective screening method for a variety of fractures.

The case records of three patients with the diagnosis pseudotumor cerebri are presented. In addition, data from the records of three other children are included to give a series of six patients. The clinical picture and the laboratory data are summarized and compared with other reports. A review of the literature is given, with emphasis on the nomenclature, etiology, clinical findings and prognosis.