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Nicotinamide riboside (NR), a form of vitamin B3 and a nicotinamide adenine dinucleotide (NAD + ) precursor, has been shown to activate the mitochondrial unfolded protein response (UPR mt ) and extend the lifespan when supplemented to C. elegans. The ketone body and histone deacetylase (HDAC) inhibitor beta-hydroxybutyrate (BHB) has also been shown to extend C. elegans lifespan. Experiments were performed that showed that NR extended lifespan by acting almost exclusively during larval development, while BHB extended lifespan by acting during adulthood, and the combination of NR during development and BHB during adulthood unexpectedly decreased lifespan. This suggests that hormesis is involved in the lifespan-altering effects of BHB and NR and that they are inducing parallel longevity pathways that converge on a common downstream target., Competing Interests: The authors declare that there are no conflicts of interest present., (Copyright: © 2023 by the authors.)

Aluminum gallium arsenide (AlGaAs) and related III-V semiconductors have excellent optoelectronic properties. They also possess strong material nonlinearity as well as high refractive indices. In view of these properties, AlGaAs is a promising candidate for integrated photonics, including both linear and nonlinear devices, passive and active devices, and associated applications. Low propagation loss is essential for integrated photonics, particularly in nonlinear applications. However, achieving low-loss and high-confinement AlGaAs photonic integrated circuits poses a challenge. Here we show an effective reduction of surface-roughness-induced scattering loss in fully etched high-confinement AlGaAs-on-insulator nanowaveguides by using a heterogeneous wafer-bonding approach and optimizing fabrication techniques. We demonstrate ultrahigh-quality AlGaAs microring resonators and realize quality factors up to 3.52 × 10 6 and finesses as high as 1.4 × 10 4 . We also show ultra-efficient frequency comb generations in those resonators and achieve record-low threshold powers on the order of ∼20 µW and ∼120 µW for the resonators with 1 THz and 90 GHz free-spectral ranges, respectively. Our result paves the way for the implementation of AlGaAs as a novel integrated material platform specifically for nonlinear photonics and opens a new window for chip-based efficiency-demanding practical applications.

The demand for low-noise, continuous-wave, frequency-tunable lasers based on semiconductor integrated photonics has advanced in support of numerous applications. In particular, an important goal is to achieve a narrow spectral linewidth, commensurate with bulk-optic or fiber-optic laser platforms. Here we report on laser-frequency-stabilization experiments with a heterogeneously integrated III/V-Si widely tunable laser and a high-finesse, thermal-noise-limited photonic resonator. This hybrid architecture offers a chip-scale optical-frequency reference with an integrated linewidth of 60 Hz and a fractional frequency stability of 2.5×10 -13 at 1 s integration time. We explore the potential for stabilization with respect to a resonator with lower thermal noise by characterizing laser-noise contributions such as residual amplitude modulation and photodetection noise. Widely tunable, compact and integrated, cost-effective, stable, and narrow-linewidth lasers are envisioned for use in various fields, including communication, spectroscopy, and metrology.

Recent advances in nonlinear optics have revolutionized integrated photonics, providing on-chip solutions to a wide range of new applications. Currently, state of the art integrated nonlinear photonic devices are mainly based on dielectric material platforms, such as Si 3 N 4 and SiO 2 . While semiconductor materials feature much higher nonlinear coefficients and convenience in active integration, they have suffered from high waveguide losses that prevent the realization of efficient nonlinear processes on-chip. Here, we challenge this status quo and demonstrate a low loss AlGaAs-on-insulator platform with anomalous dispersion and quality (Q) factors beyond 1.5 × 10 6 . Such a high quality factor, combined with high nonlinear coefficient and small mode volume, enabled us to demonstrate a Kerr frequency comb threshold of only ∼36 µW in a resonator with a 1 THz free spectral range, ∼100 times lower compared to that in previous semiconductor platforms. Moreover, combs with broad spans (>250 nm) have been generated with a pump power of ∼300 µW, which is lower than the threshold power of state-of the-art dielectric micro combs. A soliton-step transition has also been observed for the first time in an AlGaAs resonator.

In this contribution, we investigate the impact of lateral leakage for linear and nonlinear optical waveguides in lithium niobate on an insulator (LNOI). Silicon nitride (SiN) loaded and direct patterned lithium niobate cross-sections are investigated. We show that lateral leakage can take place for the TE mode in LNOI ridge waveguides (X-cut lithium niobate), due to the birefringence of the material. This work gives guidelines for designing waveguides in LNOI that do not suffer from the lateral leakage effect. By applying these design considerations, we avoided the lateral leakage effect at the second harmonic wavelength of a nonlinear optical waveguide in LNOI and demonstrate a peak second harmonic generation conversion efficiency of ~1160% W -1 cm -2 .

In this Letter, we demonstrate a low loss gallium arsenide and aluminum gallium arsenide on an insulator platform by heterogenous integration. The resonators on this platform exhibit record high quality factors up to 1.5×10 6 , corresponding to a propagation loss ∼0.4  dB/cm. For the first time, to the best of our knowledge, the loss of integrated III-V semiconductor on insulator waveguides becomes comparable with that of the silicon-on-insulator waveguides. This Letter should have a significant impact on photonic integrated circuits (PICs) and become an essential building block for the evolving nonlinear PICs and integrated quantum photonic systems in the future.

A wafer-level and high-efficiency radio frequency (RF) testing of a photonic device is highly desired in the fabrication and characterization of large-scale photonic integration circuits. In this work, we propose on-wafer probing kit designs, and demonstrate a damage-free, self-calibrated RF characterization of an integrated silicon photonic transceiver with a heterodyne mixing approach. Reduced or even free of fiber coupling off chip operation can be achieved with the on-wafer probing-kit to extract the frequency responses of broadband modulators and photodetectors in the photonic integration transceiver, with no requirement of electro-optical or opto-electrical calibration. A proof-of-concept probing kit is designed and fabricated with an on-chip electroabsorption modulator (EAM) and photodetectors by heterogeneously integrated III-V material on silicon substrate. On-wafer RF measurements with the self-calibration method are experimentally demonstrated with an accuracy analysis compared with the conventional swept-frequency method. The on-wafer and full-electrical test nature of the probing kit significantly advances performance monitoring of photonic integration circuits during chip fabrication, and promisingly offers predictable outcome and yield analysis before packaging.

An ideal photonic integrated circuit for nonlinear photonic applications requires high optical nonlinearities and low loss. This work demonstrates a heterogeneous platform by bonding lithium niobate (LN) thin films onto a silicon nitride (Si 3 N 4 ) waveguide layer on silicon. It not only provides large second- and third-order nonlinear coefficients, but also shows low propagation loss in both the Si 3 N 4 and the LN-Si 3 N 4 waveguides. The tapers enable low-loss-mode transitions between these two waveguides. This platform is essential for various on-chip applications, e.g., modulators, frequency conversions, and quantum communications.

Most studies of the mean-free path accumulation function (MFPAF) rely on optical techniques to probe heat transfer at length scales on the order of the phonon mean-free path. In this paper, we propose and implement a purely electrical probe of the MFPAF that relies on photo-lithographically defined heater-thermometer separation to set the length scale. An important advantage of the proposed technique is its insensitivity to the thermal interfacial impedance and its compatibility with a large array of temperature-controlled chambers that lack optical ports. Detailed analysis of the experimental data based on the enhanced Fourier law (EFL) demonstrates that heat-carrying phonons in gallium arsenide have a much wider mean-free path spectrum than originally thought.

In this paper we demonstrate highly linear Mach-Zehnder interferometer modulators utilizing heterogeneous integration on a Si substrate (HS-MZM). A record high dynamic range was achieved for silicon devices, obtained using hybrid III-V/Si phase modulation sections and single drive push-pull operation, demonstrating a spurious free dynamic range (SFDR) of 112 dB∙Hz 2/3 at 10 GHz, comparable to commercial Lithium Niobate MZMs.

Objectives: To identify factors predicting use, adherence and attrition with a nurse-moderated web-based group intervention designed to support mothers of infants aged 0-6 months., Design: 9-Month observational study., Setting: Community maternal and child health service., Participants: 240 mothers attending initial postnatal health checks at community clinics who were randomly assigned to the intervention arm of a pragmatic preference randomised trial (total randomised controlled trial, n=819; response rate=45%)., Intervention: In the first week (phase I), mothers were assisted with their first website login by a research assistant. In weeks 2-7 (phase II), mothers participated in the web-based intervention with an expectation of weekly logins. The web-based intervention was comparable to traditional face-to-face new mothers' groups. During weeks 8-26 (phase III), mothers participated in an extended programme at a frequency of their choosing., Primary Outcome Measures: Number of logins and posted messages. Standard self-report measures assessed maternal demographic and psychosocial characteristics., Results: In phase II, the median number of logins was 9 logins (IQR=1-25), and in phase III, it was 10 logins (IQR=0-39). Incident risk ratios from multivariable analyses indicated that compared to mothers with the lowest third of logins in phase I, those with the highest third had 6.43 times as many logins in phase II and 7.14 times in phase III. Fifty per cent of mothers logged-in at least once every 30 days for 147 days after phase I and 44% logged-in at least once in the last 30 days of the intervention. Frequency of logins during phase I was a stronger predictor of mothers' level of engagement with the intervention than their demographic and psychosocial characteristics., Conclusions: Mothers' early use of web-based interventions could be employed to customise engagement protocols to the circumstances of individual mothers with the aim of improving adherence and reducing attrition with web-based interventions., Trial Registration Number: ACTRN12613000204741; Results., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Psychiatric co-management is often required in HIV primary care. While rates and clinical impact of linkage and retention in HIV are well explored, fewer investigations focus specifically on linkage to psychiatry. In this investigation, we evaluate factors associated with linkage to psychiatric services using a retrospective cohort study of HIV-infected patients during a two-year observation period. Descriptive statistics depict patient characteristics, and logistic regression models were fit to evaluate factors associated with failure to establish care at the co-located psychiatry clinic following referral from HIV provider. Of 370 referred, 23 % did not attend a scheduled psychiatry appointment within 6 months of initial referral. In multivariable analysis, Non-white race, younger age, non-suppressed viral load, and increased wait time to appointment (in days) were associated with failure to attend. Further exploration of barriers that contribute to disparate linkage to psychiatric care may inform future interventions to improve HIV outcomes in this population.

In this work we present the first fully-integrated free-space beam-steering chip using the hybrid silicon platform. The photonic integrated circuit (PIC) consists of 164 optical components including lasers, amplifiers, photodiodes, phase tuners, grating couplers, splitters, and a photonic crystal lens. The PIC exhibited steering over 23° x 3.6° with beam widths of 1° x 0.6°.

Background: Stenosing tenosynovitis or trigger finger is a common clinical condition regularly treated with steroid injections. Varied success is reported at early time points following injection. We present a prospective, randomized IRB-approved study to confirm these findings at a long-term follow-up., Methods: Adult patients presenting with symptoms of stenosing tenosynovitis who agreed to participate were randomized into two groups. Group 1 received an initial injection of triamcinolone and local anesthetic mixture. Group 2 received the same initial injection and an additional staged injection at 6 weeks. The patients were then followed beyond 2 years. If Group 1 patients were still symptomatic at 6 weeks, another injection was given. An additional injection or surgery was defined as treatment failure. DASH scores were obtained at baseline, 3, 6, and 12 months., Results: Ninety-seven patients (101 trigger digits) were enrolled in the prospective trial. Fifty-six digits were randomized to the one-injection group versus 45 digits randomized to the two-injection group ("intention to treat analysis"-ITT). After accounting for crossover between the groups, 42 patients received one-injection versus fifty-nine patients receiving two injections ("actual" analysis). Overall failure was the same between the two groups. However, a higher surgery rate was noted for patients having undergone two injections versus one injection [47 % versus 27 % (p < 0.013), ITT]. Diabetes was associated with a higher surgery rate at 1 year within the group of overall failures [56 % versus 37 % (p = 0.0505), ITT]. High baseline DASH score (>40) was associated with a median time of 10 months for failure and 6 months for surgery as per a Kaplan-Meier survival analysis (p < 0.005 and p < 0.001, respectively, ITT)., Conclusions: As overall failure of steroid injection for trigger finger is not improved with staged, two-injection treatment, we recommend a single injection initial treatment for trigger finger with a second injection given in cases of recurrence or failure. Diabetes was a risk factor for needing surgery if failure occurred within 1 year. The baseline DASH score is helpful in predicting which patients have a higher chance of failing as well as needing surgery. Level of evidence Prospective, randomized trial, level I.

This study reports the incidence, risk factors, and functional outcomes of the largest reported series of patients treated arthroscopically for patella clunk syndrome (PCS). All patients treated arthroscopically for PCS were identified. Patients were matched with controls by sex and date of surgery. Follow-up was conducted using SF-12 and WOMAC questionnaires. Operative notes and preoperative and postoperative radiographs were reviewed. Seventy-five knees in 68 patients were treated arthroscopically for PCS. Average follow-up was 4.2 years. Functional scores demonstrated no statistical difference. PCS patients had a significantly more valgus preoperative alignment, greater change in posterior femoral offset and smaller patellar component size. PCS is a relatively common complication following TKA. Arthroscopy yields functional results comparable to controls. Radiographic and technical factors are associated with PCS., (Copyright © 2014 Elsevier Inc. All rights reserved.)

A broadband superluminescent III-V-on-silicon light-emitting diode (LED) was realized. To achieve the large bandwidth, quantum well intermixing and multiple die bonding of InP on a silicon photonic waveguide circuit were combined for the first time, to the best of our knowledge. The device consists of four sections with different bandgaps, centered around 1300, 1380, 1460, and 1540 nm. The fabricated LEDs were connected on-chip in a serial way, where the light generated in the smaller bandgap sections travels through the larger bandgap sections. By balancing the pump current in the four LEDs, we achieved 292 nm of 3 dB bandwidth and an on-chip power of -8  dBm.

A chip-scale optical source with integrated beam steering is demonstrated. The chip was fabricated using the hybrid silicon platform and incorporates an on-chip laser, waveguide splitter, amplifiers, phase modulators, and surface gratings to comprise an optical phased array with beam steering across a 12° field of view in one axis. Tuning of the phased array is used to achieve 1.8°(steered axis)×0.6°(nonsteered axis) beam width with 7 dB background suppression for arbitrary beam direction within the field of view.

A monolithic 25 Gbaud DQPSK receiver based on delay interferometers and balanced detection has been designed and fabricated on the hybrid Si/InGaAs platform. The integrated 30 µm long InGaAs p-i-n photodetectors have a responsivity of 0.64 A/W at 1550 nm and a 3dB bandwidth higher than 25 GHz. The delay interferometer shows a delay time of 39.2 ps and an extinction ratio higher than 20 dB. The demodulation of a 25 Gb/s DPSK signal by a single branch of the receiver demonstrates its correct working principle.

A distributed III-V-on-Si electroabsorption modulator based on an asymmetric segmented electrode has been developed on the hybrid silicon platform for the 1.3 μm transmission window. The measured modulation response shows a 2 dB drop at 67 GHz and an extrapolated 3 dB bandwidth of 74 GHz. Large signal measurements show clearly open eye diagrams at 50 Gb/s. An extinction ratio of 9.6 dB for back to back transmission and an extinction ratio of 9.4 dB after 16 km transmission were obtained with a drive voltage of 2.2 V.

We demonstrate a 16-channel, independently tuned waveguide surface grating optical phased array in silicon for two dimensional beam steering with a total field of view of 20° x 14°, beam width of 0.6° x 1.6°, and full-window background peak suppression of 10 dB., (© 2011 Optical Society of America)

We have demonstrated a traveling-wave electroabsorption modulator based on the hybrid silicon platform. For a device with a 100 μm active segment, the small-signal electro/optical response renders a 3 dB bandwidth of around 42 GHz and its modulation efficiency reaches 23 GHz/V. A dynamic extinction ratio of 9.8 dB with a driving voltage swing of only 2 V was demonstrated at a transmission rate of 50 Gb/s. This represents a significant improvement for modulators compatible with integration of silicon-based photonic integrated circuits.

We demonstrate a hybrid silicon modulator operating up to 40 Gb/s with 11.4 dB extinction ratio. The modulator has voltage-length product of 2.4 V-mm and chirp of -0.75 over the entire bias range. As a switch, it has a switching time less than 20 ps.

The impact of sleep restriction on sustained attention in children has not been well quantified. To address this shortcoming, this study tested the sensitivity of a 5-min personal digital assistant-psychomotor vigilance task (PDA-PVT) to sleep restriction in 14 female children [mean (SD) age = 10.6 +/- 0.3 years]. The children underwent PDA-PVT trials at regular intervals both before and after a sleep restriction (5 h time-in-bed) and a control (10 h time-in-bed) condition. Sleep restriction was associated with longer mean response times and increased number of lapses. These results are consistent with findings in the adult literature suggesting an association between inadequate sleep and impaired functioning. In conclusion, the 5-min PDA-PVT is sensitive to sleep restriction in pre-adolescent female children supporting the utility of the PDA-PVT for examining the impact of sleep deprivation on daytime functioning in children.

Prolonged sleep deprivation is stressful and has been associated with adverse consequences for health and cognitive performance. Here, we show that sleep deprivation inhibits adult neurogenesis at a time when circulating levels of corticosterone are elevated. Moreover, clamping levels of this hormone prevents the sleep deprivation-induced reduction of cell proliferation. The recovery of normal levels of adult neurogenesis after chronic sleep deprivation occurs over a 2-wk period and involves a temporary increase in new neuron formation. This compensatory increase is dissociated from glucocorticoid levels as well as from the restoration of normal sleep patterns. Collectively, these findings suggest that, although sleep deprivation inhibits adult neurogenesis by acting as a stressor, its compensatory aftereffects involve glucocorticoid-independent factors.

Maternal deprivation produces persistent abnormalities in behavioral and neuroendocrine functions associated with the hippocampus, a brain region that shows considerable structural change in response to experience throughout life. Here we show that adverse experience early in life affects the regulation of adult neurogenesis in the hippocampus. More specifically, a decrease in cell proliferation and immature neuron production are observed in the dentate gyrus of adult rats that are maternally separated as pups. Although maternally separated rats show normal basal levels of corticosterone, the suppression of cell proliferation in these rats can be reversed by lowering corticosterone below the control value. In addition, normal stress-induced suppression of cell proliferation and neurogenesis, despite normal activation of the hypothalamic pituitary adrenal (HPA) axis, is not observed in maternally separated rats. Our results suggest that early adverse experience inhibits structural plasticity via hypersensitivity to glucocorticoids and diminishes the ability of the hippocampus to respond to stress in adulthood.

Homologous desensitization of D(1) dopamine receptors is thought to occur through their phosphorylation leading to arrestin association which interdicts G protein coupling. In order to identify the relevant domains of receptor phosphorylation, and to determine how this leads to arrestin association, we created a series of mutated D(1) receptor constructs. In one mutant, all of the serine/threonine residues within the 3rd cytoplasmic domain were altered (3rdTOT). A second construct was created in which only three of these serines (serines 256, 258, and 259) were mutated (3rd234). We also created four truncation mutants of the carboxyl terminus (T347, T369, T394, and T404). All of these constructs were comparable with the wild-type receptor with respect to expression and adenylyl cyclase activation. In contrast, both of the 3rd loop mutants exhibited attenuated agonist-induced receptor phosphorylation that was correlated with an impaired desensitization response. Sequential truncation of the carboxyl terminus of the receptor resulted in a sequential loss of agonist-induced phosphorylation. No phosphorylation was observed with the most severely truncated T347 mutant. Surprisingly, all of the truncated receptors exhibited normal desensitization. The ability of the receptor constructs to promote arrestin association was evaluated using arrestin-green fluorescent protein translocation assays and confocal fluorescence microscopy. The 3rd234 mutant receptor was impaired in its ability to induce arrrestin translocation, whereas the T347 mutant was comparable with wild type. Our data suggest a model in which arrestin directly associates with the activated 3rd cytoplasmic domain in an agonist-dependent fashion; however, under basal conditions, this is sterically prevented by the carboxyl terminus of the receptor. Receptor activation promotes the sequential phosphorylation of residues, first within the carboxyl terminus and then the 3rd cytoplasmic loop, thereby dissociating these domains and allowing arrestin to bind to the activated 3rd loop. Thus, the role of receptor phosphorylation is to allow access of arrestin to its receptor binding domain rather than to create an arrestin binding site per se.

Background: Condensation occurs rapidly on intraocular lenses (IOLs), particularly silicone IOLs, after vitrectomy and fluid-air exchange in the presence of a posterior capsulotomy and severely limits the surgeon's view of the retina. This study investigated the value of heating contact lens irrigation fluid to prevent condensation on IOLs., Design: An experimental in vitro study and a noncomparative interventional case series., Participants: Five control eyes had temperature measurements during fluid-air exchanges. Two patients with silicone IOLs and posterior capsulotomies underwent a vitrectomy involving a fluid-air exchange with heated contact lens fluid., Methods: An in vitro model allowed monitoring of temperature and humidity changes during condensation formation on four different IOL materials. Adjusting variables to promote evaporation rather than condensation was achieved in vitro. In vivo, intraocular temperatures were measured at various stages of five vitrectomies involving a fluid-air exchange. Finally, in two in vivo cases a blood warmer was used to heat the accessory contact lens irrigation fluid during the vitrectomy and fluid-air exchange., Main Outcome Measures: Successful prevention of condensation on the silicone IOL during the fluid-air exchange., Results: Anterior segment temperature influences the IOL temperature, such that when it is higher than the posterior segment temperature, condensation does not form and evaporation is promoted. In vivo the temperatures in the eye are hypothermic throughout the vitrectomy. At fluid-air exchange the posterior segment heats rapidly as irrigation ceases and low specific heat gas enters. Finally, in two in vivo cases with silicone IOLs, condensation was predicted then prevented by our intervention for the duration of the fluid-air exchange., Conclusions: Heating the anterior segment by conduction from warmed irrigation fluid flowing through the irrigating contact lens represents a cheap, noninvasive, and safe means to prevent condensation on IOL materials.

Aggregation of the B-cell antigen receptor leads to the activation of the 72-kDa Syk protein-tyrosine kinase and the phosphorylation of tubulin on tyrosine. To explore the requirement of Syk catalytic activity for tubulin phosphorylation, tubulin was isolated from cytosolic fractions from anti-IgM-activated B-cells (DT40) that lacked endogenous Syk and immunoblotted with anti-phosphotyrosine antibodies. Tubulin was not tyrosine-phosphorylated in Syk- B-cells. Phosphorylation could be restored by the expression of wild-type, but not catalytically inactive, Syk. However, both catalytically inactive and wild-type Syk were capable of constitutive association with tubulin, indicating that tubulin phosphorylation is not required for this interaction. Anti-phosphotyrosine antibody immunoblotting of proteins adsorbed to colchicine-agarose revealed the presence of three major tubulin-associated phosphoproteins of 110, 90, and 74 kDa, the phosphorylation of which was dependent on Syk expression. The proteins of 110 and 90 kDa were identified as Cbl and Vav, two proto-oncogene products known to become prominently phosphorylated following receptor engagement. Both proteins were shown to be constitutively associated with tubulin.

Syk (p72syk) is a 72-kDa, nonreceptor, protein-tyrosine kinase that becomes tyrosine-phosphorylated and activated in B lymphocytes following aggregation of the B-cell antigen receptor. To explore the subcellular location of activated Syk, anti-IgM-activated B-cells were fractionated into soluble and particulate fractions by ultracentrifugation. Activated and tyrosine-phosphorylated Syk was found predominantly in the soluble fraction and was not associated with components of the antigen receptor. Similarly, the activated forms of Syk and its homolog, ZAP-70, were found in soluble fractions prepared from pervanadate-treated Jurkat T-cells. A 54-kDa protein that co-immunoprecipitated with Syk from the soluble fraction of activated B-cells was identified by peptide mapping as alpha-tubulin. alpha-Tubulin was an excellent in vitro substrate for Syk and was phosphorylated on a single tyrosine present within an acidic stretch of amino acids located near the carboxyl terminus. alpha-Tubulin was phosphorylated on tyrosine in intact cells following aggregation of the B-cell antigen receptor in a reaction that was inhibited by the Syk-selective inhibitor, piceatannol. Thus, once activated, Syk releases from the aggregated antigen receptor complex and is free to associate with and phosphorylate soluble proteins including alpha-tubulin.

The authors have reviewed the records of 36 patients with idiopathic scoliosis who underwent a single-stage anterior spinal fusion with Zielke instrumentation to determine if any adverse frontal or secondary sagittal deformities or changes in balance resulted from the surgery. Spontaneous correction of uninstrumented thoracic curves was noted in five patients with double-major curves, and frontal balance was maintained or improved after operation in all but four patients. Kyphosis was increased in the instrumented segments in all patients. In the uninstrumented segments, however, thoracic kyphosis and lumbar lordosis were decreased in all but five patients after operation, whereas overall sagittal balance was not adversely affected by the surgery in any patient.

Thirty-one cases of failed metal-backed patellar components requiring revision surgery are reviewed. Two modes of implant failure onset were noted. Within each group, delays in patient presentation and diagnosis of the failed component were encountered. The syndrome of the failed metal-backed patellar component is proposed. The authors conclude that: (1) more of these failures will be seen in the future; (2) this patient population needs appropriate counsel concerning the signs and symptoms of this syndrome as well as more frequent follow-up evaluations; (3) surgeons treating this complication should be prepared to revise all components; and (4) the use of metal-backed patellar components should be discontinued.

Twelve cases of adult anisomelia were treated with closed intramedullary femoral shortening. Follow-up was conducted at regular intervals until the osteotomy healed. This study reviewed hospital and office records, preoperative and postoperative roentgenograms, and telephone interviews of all patients. An average femoral shortening of 3.7 cm was attained; significant complications such as deep infection or nonunion did not occur. These results suggest that closed intramedullary shortening of the femur produces excellent results in cases of adult anisomelia.

Purulent pericarditis is a serious but uncommon disorder which rarely complicates acute myocardial infarction. We have described a patient who had fatal purulent pericarditis subsequent to Swan-Ganz catheterization, which was done to facilitate the management of left ventricular failure complicating acute myocardial infarction. Although rare, purulent pericarditis should be considered in the differential diagnosis of otherwise unexplained sepsis associated with myocardial infarction. The presence of a pericardial effusion may rapidly be confirmed by echocardiography, and diagnostic pericardiocentesis undertaken.

Historically, hospital liability for the wrongful acts of physicians was based on the doctrine of vicarious liability-i.e., the physician was regarded as an employee or agent of the hospital. With the courts' growing recognition of most physicians as independent contractors, the doctrine of corporate or direct liability has emerged as the primary basis upon which courts now hold hospitals liable for failing to adequately monitor and control the standards of medical care and treatment offered within their walls. This article discusses eleven theories for imposing direct liability on hospitals and considers their impact on hospital-physician relations.