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Entanglement in multipartite systems is a key resource for quantum information and communication protocols, making its verification in complex systems a necessity. Because an exact calculation of arbitrary entanglement probes is impossible, we derive and implement a numerical method to construct multipartite witnesses to uncover entanglement in arbitrary systems. Our technique is based on a substantial generalization of the power iteration—an essential tool for computing eigenvalues—and it is a solver for the separability eigenvalue equations, enabling the general formulation of optimal entanglement witnesses. Beyond our rigorous derivation and direct implementation of this method, we apply our approach to several examples of complexly quantum-correlated states and benchmark its general performance. Consequently, we provide a generally applicable numerical tool for the identification of multipartite entanglement.

NMR chemical shift tensors (CSTs) in proteins, as well as their orientations, represent an important new restraint class for protein structure refinement and determination. Here, we present the first determination of both CST magnitudes and orientations for 13Cα and 15N (peptide backbone) groups in a protein, the β1 IgG binding domain of protein G from Streptococcus spp., GB1. Site-specific 13Cα and 15N CSTs were measured using synchronously evolved recoupling experiments in which 13C and 15N tensors were projected onto the 1H-13C and 1H-15N vectors, respectively, and onto the 15N-13C vector in the case of 13Cα. The orientations of the 13Cα CSTs to the 1H-13C and 13C-15N vectors agreed well with the results of ab initio calculations, with an rmsd of approximately 8°. In addition, the measured 15N tensors exhibited larger reduced anisotropies in α-helical versus β-sheet regions, with very limited variation (18 ± 4°) in the orientation of the z-axis of the 15N CST with respect to the 1H-15N vector. Incorporation of the 13Cα CST restraints into structure calculations, in combination with isotropic chemical shifts, transferred echo double resonance 13C-15N distances and vector angle restraints, improved the backbone rmsd to 0.16 Å (PDB ID code 2LGI) and is consistent with existing X-ray structures (0.51 Å agreement with PDB ID code 2QMT). These results demonstrate that chemical shift tensors have considerable utility in protein structure refinement, with the best structures comparable to 1.0-Å crystal structures, based upon empirical metrics such as Ramachandran geometries and χ1/χ2 distributions, providing solid-state NMR with a powerful tool for de novo structure determination.

Solid-state NMR has emerged as an important tool for structural biology and chemistry, capable of solving atomic-resolution structures for proteins in membrane-bound and aggregated states. Proton detection methods have been recently realized under fast magic-angle spinning conditions, providing large sensitivity enhancements for efficient examination of uniformly labeled proteins. The first and often most challenging step of protein structure determination by NMR is the site-specific resonance assignment. Here we demonstrate resonance assignments based on high-sensitivity proton-detected three-dimensional experiments for samples of different physical states, including a fully-protonated small protein (GB1, 6 kDa), a deuterated microcrystalline protein (DsbA, 21 kDa), a membrane protein (DsbB, 20 kDa) prepared in a lipid environment, and the extended core of a fibrillar protein (α-synuclein, 14 kDa). In our implementation of these experiments, including CONH, CO(CA)NH, CANH, CA(CO)NH, CBCANH, and CBCA(CO)NH, dipolar-based polarization transfer methods have been chosen for optimal efficiency for relatively high protonation levels (full protonation or 100 % amide proton), fast magic-angle spinning conditions (40 kHz) and moderate proton decoupling power levels. Each H–N pair correlates exclusively to either intra- or inter-residue carbons, but not both, to maximize spectral resolution. Experiment time can be reduced by at least a factor of 10 by using proton detection in comparison to carbon detection. These high-sensitivity experiments are especially important for membrane proteins, which often have rather low expression yield. Proton-detection based experiments are expected to play an important role in accelerating protein structure elucidation by solid-state NMR with the improved sensitivity and resolution.

We evaluated signal-noise discrimination in children with and without dyslexia, using magnocellular and parvocellular visual stimuli presented either with or without high noise. Dyslexic children had elevated contrast thresholds when stimuli of either type were presented in high noise, but performed as well as non-dyslexic children when either type was displayed without noise. Our findings suggest that deficits in noise exclusion, not magnocellular processing, contribute to the etiology of dyslexia.

Seventy-eight Neer hemiarthroplasties and thirty-six Neer total shoulder arthroplasties were performed at our institution, between January 1, 1976, and December 31, 1985, in ninety-eight patients who were fifty years old or less. Two patients (two shoulders) died, and four patients (four shoulders) were lost to follow-up. The remaining seventy-four hemiarthroplasties (95 per cent) in sixty-four patients and thirty-four total shoulder arthroplasties (94 per cent) in thirty-one patients were included in the clinical analysis as the preoperative and operative records were complete and the patients had been followed for at least five years (mean, 12.3 years) or until revision. All 114 shoulders were included in the survivorship analysis. Both total shoulder arthroplasty and hemiarthroplasty resulted in significant long-term relief of pain (p < 0.0001) as well as improvement in active abduction (p < 0.0001) and external rotation (p < 0.0001). However, with the numbers available, we could not detect a significant difference between the two procedures with respect to these variables. A complete set of radiographs was available for sixty-eight (92 per cent) of the seventy-four shoulders that had a hemiarthroplasty and for thirty-two (94 per cent) of the thirty-four shoulders that had a total shoulder arthroplasty. A radiolucent line around the humeral component was noted after sixteen (24 per cent) of the hemiarthroplasties and after seventeen (53 per cent) of the total shoulder arthroplasties. A radiolucent line around the glenoid component was seen after nineteen (59 per cent) of the total shoulder arthroplasties. Erosion of the glenoid was found after forty-six (68 per cent) of the hemiarthroplasties. The results were graded according to a modification of the system of Neer et al. and of Cofield. Fifteen hemiarthroplasties led to an excellent result; twenty-four, a satisfactory result; and thirty-five, an unsatisfactory or unsuccessful result. Four total shoulder arthroplasties were followed by an excellent result; thirteen, a satisfactory result; and seventeen, an unsatisfactory or unsuccessful result. The estimated survival of the hemiarthroplasty prostheses (with 95 per cent confidence intervals) was 92 per cent (86 to 98 per cent) at five years, 83 per cent (75 to 93 per cent) at ten years, and 73 per cent (59 to 88 per cent) at fifteen years. Analysis of the results in association with the two major diagnoses revealed that the risk of revision was higher for the thirty shoulders that had the hemiarthroplasty for the treatment of the sequelae of trauma than for the twenty-eight that had the procedure for the treatment of rheumatoid arthritis (p = 0.017). The estimated survival of the total shoulder prostheses (with 95 per cent confidence intervals) was 97 per cent (92 to 100 per cent) at five years, 97 per cent (91 to 100 per cent) at ten years, and 84 per cent (70 to 100 per cent) at fifteen years. The risk of revision was higher for the seven shoulders that had had a tear of the rotator cuff at the time of the operation than for the twenty-seven that had not had one (p = 0.029). The data from the present study indicate that a shoulder arthroplasty provides marked long-term relief of pain and improvement in motion; however, nearly half of all young patients who have a shoulder arthroplasty have an unsatisfactory result according to a rating system. Care should be exercised when either a hemiarthroplasty or a total shoulder arthroplasty is offered to patients who are fifty years old or less.

Magnetic resonance imaging (MRI) enables high-resolution non-invasive observation of the anatomy and function of intact organisms. However, previous MRI reporters of key biological processes tied to gene expression have been limited by the inherently low molecular sensitivity of conventional 1 H MRI. This limitation could be overcome through the use of hyperpolarized nuclei, such as in the noble gas xenon, but previous reporters acting on such nuclei have been synthetic. Here, we introduce the first genetically encoded reporters for hyperpolarized 129 Xe MRI. These expressible reporters are based on gas vesicles (GVs), gas-binding protein nanostructures expressed by certain buoyant microorganisms. We show that GVs are capable of chemical exchange saturation transfer interactions with xenon, which enables chemically amplified GV detection at picomolar concentrations (a 100- to 10,000-fold improvement over comparable constructs for 1 H MRI). We demonstrate the use of GVs as heterologously expressed indicators of gene expression and chemically targeted exogenous labels in MRI experiments performed on living cells. Magnetic resonance imaging of gene expression has been limited by the low molecular sensitivity of conventional 1 H-MRI. To overcome this limitation, the first genetically encoded reporters for hyperpolarized xenon MRI have been developed. These expressible reporters, based on gas-filled protein nanostructures from buoyant microorganisms, are detectable at picomolar concentrations.

Magic-angle spinning solid-state NMR (MAS SSNMR) represents a fast developing experimental technique with great potential to provide structural and dynamics information for proteins not amenable to other methods. However, few automated analysis tools are currently available for MAS SSNMR. We present a methodology for automating protein resonance assignments of MAS SSNMR spectral data and its application to experimental peak lists of the β1 immunoglobulin binding domain of protein G (GB1) derived from a uniformly 13 C- and 15 N-labeled sample. This application to the 56 amino acid GB1 produced an overall 84.1% assignment of the N, CO, CA, and CB resonances with no errors using peak lists from NCACX 3D, CANcoCA 3D, and CANCOCX 4D experiments. This proof of concept demonstrates the tractability of this problem.

BackgroundCurrently, there is little information concerning periprosthetic humeral fractures after shoulder arthroplasty. Therefore, we reviewed our experience with these fractures to determine the results of treatment, the risk factors for periprosthetic fracture, and the rates of reoperation.MethodsBetween 1976 and 2001, nineteen postoperative periprosthetic humeral fractures occurred among 3091 patients who had undergone shoulder arthroplasty at our institution. Sixteen patients had a complete series of radiographs and were included in this study. The average time from the arthroplasty to the fracture was forty-nine months. Seven patients had severe osteopenia. Twelve fractures occurred at the tip of the prosthesis; of these, six extended proximally (type-A fractures) and six did not (type-B fractures). Three fractures occurred distal to the implant and extended into the distal humeral metaphysis (type-C fractures). One fracture occurred in the proximal metadiaphyseal region because of osteolysis.ResultsSix fractures healed after an average of 180 days of nonoperative treatment. Five fractures were treated operatively after an average of 123 days of unsuccessful nonoperative treatment. The remaining five fractures had immediate operative treatment. All sixteen fractures healed. One patient required multiple operations over a period of three years before union was achieved. With the exclusion of this patient and one other patient who received a custom prosthesis, the average time between the first operative procedure and union was 278 days.ConclusionsOur data do not clearly indicate the need for operative treatment of type-A fractures unless the humeral component is loose. A trial of nonoperative treatment may be considered for well-aligned type-B fractures that are associated with a well-fixed humeral component; however, operative intervention should be considered for type-B fractures that have not progressed toward union by three months. If the component is well fixed, open reduction and internal fixation may be performed. If the component is loose, revision with a long-stem component is recommended. For type-C fractures, a trial of nonoperative treatment is recommended.Level of EvidenceTherapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Although temporal lobe epilepsy (TLE) and resection (TLR) impact olfactory eloquent brain structures, their influences on olfaction remain enigmatic. We sought to more definitively assess the influences of TLE and TLR on olfaction using three well-validated olfactory tests and measuring the tests’ associations with the volume of numerous temporal lobe brain structures. The University of Pennsylvania Smell Identification Test and an odor detection threshold test were administered to 71 TLE patients and 71 age- and sex-matched controls; 69 TLE patients and controls received an odor discrimination/memory test. Fifty-seven patients and 57 controls were tested on odor identification and threshold before and after TLR; 27 patients and 27 controls were similarly tested for odor detection/discrimination. Scores were compared using analysis of variance and correlated with pre- and post-operative volumes of the target brain structures. TLE was associated with bilateral deficits in all test measures. TLR further decreased function on the side ipsilateral to resection. The hippocampus and other structures were smaller on the focus side of the TLE subjects. Although post-operative volumetric decreases were evident in most measured brain structures, modest contralateral volumetric increases were observed in some cases. No meaningful correlations were evident pre- or post-operatively between the olfactory test scores and the structural volumes. In conclusion, we demonstrate that smell dysfunction is clearly a key element of both TLE and TLR, impacting odor identification, detection, and discrimination/memory. Whether our novel finding of significant post-operative increases in the volume of brain structures contralateral to the resection side reflects plasticity and compensatory processes requires further study.

The development of painful glenoid arthrosis is the most common reason for reoperation after replacement of the humeral head. We performed twenty-two revision total shoulder arthroplasties, between 1983 and 1992, for the treatment of painful glenoid arthrosis in shoulders that had a prosthetic replacement of the humeral head. Eighteen shoulders (seventeen patients) were included in the study as their preoperative and operative records were complete and they had been followed for at least two years (mean, 5.5 years; range, 2.3 to 10.0 years). The indications for the hemiarthroplasty were trauma (ten shoulders), osteoarthrosis (four), rheumatoid arthritis (two), and osteonecrosis secondary to the use of steroids (two). The mean interval between the hemiarthroplasty and the total shoulder replacement was 4.4 years (range, 0.8 to 12.7 years). The mean score for pain in the shoulder decreased from 4.3 points before the revision to 2.2 points after it (p = 0.0001). The mean active abduction increased from 94 degrees before the revision to 124 degrees after it (p = 0.01), and the mean external rotation increased from 32 to 58 degrees (p = 0.007). Two shoulders needed another operation after the revision because of a late infection in one and particulate synovitis associated with instability in the other. With the numbers available for study, we did not detect a significant difference in pain relief and range of motion with respect to gender, diagnosis, subluxation, or the presence of periprosthetic radiolucency. Our findings indicate that most patients with painful glenoid arthrosis after a hemiarthroplasty have marked pain relief and improvement in motion after revision to a total shoulder replacement. However, seven of the eighteen shoulders that had this procedure had an unsatisfactory result due to a limited range of motion or the need for a subsequent operation. Therefore, long-term studies are necessary to evaluate the durability of total shoulder replacement in this group of patients.