Association between spondylolisthesis and L5 fracture in patients with osteogenesis imperfecta

To investigate if an association between spondylolisthesis and L5 fracture occurs in patients affected by Osteogenesis Imperfecta (O.I.). Methods Anteroposterior and lateral radiograms were performed on the sample (38 O.I. patients, of whom 19 presenting listhesis); on imaging studies spondylolisthesis was quantified according to the Meyerding classification. Genant’s semiquantitative classification was applied on lateral view to evaluate the L5 fractures; skeleton spinal morphometry (MXA) was carried out on the same images to collect quantitative data comparable and superimposable to Genant’s classification. The gathered information were analyzed through statistical tests (O.R., χ 2 test, Fisher’s test, Pearson’s correlation coefficient). Results The prevalence of L5 fractures is 73.7 % in O.I. patients with spondylolisthesis and their risk of experiencing such a fracture is twice than O.I. patients without listhesis (OR 2.04). Pearson’s χ 2 test demonstrates an association between L5 spondylolisthesis and L5 fracture, especially with moderate, posterior fractures (p = 0.017) and primarily in patients affected by type IV O.I. Conclusions Spondylolisthesis represents a risk factor for the development of more severe and biconcave/posterior type fractures of L5 in patients suffering from O.I., especially in type IV. This fits the hypothesis that the anterior sliding of the soma of L5 alters the dynamics of action of the load forces, localizing them on the central and posterior heights that become the focus of the stress due to movement of flexion–extension and twisting of the spine. As a result, there is greater probability of developing an important subsidence of the central and posterior walls of the soma

Humoral and cellular immunopathology of hepatic and cardiac hamster-into-rat xenograft rejection: Marked stimulation of IgM^++bright/IgD^+dull splenic B cells

Normal Lewis rat serum contains antibodies (IgM > IgG) that bind to hamster leukocytes and endothelial cells. Transplantation of either the heart or liver from hamster rat results in release of hamster hematolymphoid cells from the graft, which lodge in the recipient spleen (cell migration), where recipient T- and B-cell populations initiate DNA synthesis within one day. There is marked stimulation of splenic IgM++(bright)/IgD+(dull) B cells in the marginal zone and red pulp, which account for 48% of the total splenic blast cell population by 4 days after liver transplantation. CD4+ predominant T-cell proliferation in the splenic periarterial lymphatic sheath and paracortex of peripheral lymph nodes occurs almost simultaneously. The effector phase of rejection in cardiac recipients is dominated by complement-fixing IgM antibodies, which increase daily and result in graft destruction in 3 to 4 days, even in animals treated with FK506. In liver recipients, combined antibody and cellular rejection, associated with graft infiltration by OX8+ natural killer, and fewer W3/25+ (CD4) lymphocytes, are responsible for graft failure in untreated recipients at 6 to 7 days. FK506 inhibits the T-cell response in liver recipients and significantly prolongs graft survival, but does not prevent the rise or deposition of IgM antibodies in the graft. However, a single injection of cyclophosphamide 10 days before transplantation effectively depletes the splenic IgM++(bright)/IgD+(dull) cells and in combination with FK506, results in 100% survival of both cardiac and hepatic xenografts for more than 60 days. Although extrapolation of morphological findings to functional significance is fraught with potential problems, we propose the following mechanisms of xenograft rejection. The reaction initially appears to involve primitive host defense mechanisms, including an IgM-producing subpopulation of splenic B cells and natural killer cells. Based on the reaction and distribution of OX8+ and W3/25+ cells, antibody dependent cell cytotoxicity and delayed-type hypersensitivity responses seem worthy of further investigation as possible effector mechanisms. Effective control of xenograft rejection is likely to require a dual pharmaceutical approach, one to contain T-cell immunity and another to blunt the primitive B-cell response

Resonant Processes in a Frozen Gas

We present a theory of resonant processes in a frozen gas of atoms interacting via dipole-dipole potentials that vary as $r^{-3}$, where $r$ is the interatomic separation. We supply an exact result for a single atom in a given state interacting resonantly with a random gas of atoms in a different state. The time development of the transition process is calculated both on- and off-resonance, and the linewidth with respect to detuning is obtained as a function of time $t$. We introduce a random spin Hamiltonian to model a dense system of resonators and show how it reduces to the previous model in the limit of a sparse system. We derive approximate equations for the average effective spin, and we use them to model the behavior seen in the experiments of Anderson et al. and Lowell et al. The approach to equilibrium is found to be proportional to $\exp (-\sqrt{\gamma_{eq}t}$), where the constant $\gamma _{eq}$ is explicitly related to the system's parameters.Comment: 30 pages, 6 figure

A simple noninvasive pressure–time index at the mouth to measure respiratory load during acute exacerbation of COPD A comparison with normal volunteers

AbstractWe assessed the validity of the pressure–time index (PTI) measured at the mouth as a noninvasive and simplified alternative to conventional tension–time index for assessing respiratory load and inspiratory muscle force reserve. PTI was measured within 48 h of hospital admission and at 24 h before discharge in 37 consecutive patients with acute exacerbation of chronic obstructive pulmonary disease(COPD) using the equation PTI = (Pawo/MIP)(TI/TT)100, where Pawo is the mean airway pressure measured at the mouth, MIP the maximal inspiratory pressure, andTI /TT the inspiratory time (TI) to total cycle length (TT) ratio. Controls were 30 normal volunteers with similar anthropometric features. Mean (± SD) PTI values were significantly higher in COPD patients (0.29 ± 0.10) than in controls (0.11 ± 0.04) (P<0.001) primarily because MIP and TI/TT were significantly lower and Pawo was higher in the COPD population than in controls. As a result of improvement of the respiratory condition, PTI values were significantly lower at discharge (0.20±0.10 vs. 0.29±0.10, P<0.001) due to a drop in Pawo and an increase in MIP. The accuracy of different PTI cutpoints was assessed by comparison of the receiver operating characteristics curves. Best cutpoint values for differentiating COPD patients on admission and at hospital discharge from controls were 0.13 (positive predictive value 76%) and 0.17 (positive predictive value 92%), respectively. Noninvasive PTI measured at the mouth provides a valid and easy method for assessing respiratory muscle load and reserve. Changes in PTI values reflect functional improvement following treatment of acute exacerbation of COPD

Evolution of Conversations in the Age of Email Overload

Email is a ubiquitous communications tool in the workplace and plays an important role in social interactions. Previous studies of email were largely based on surveys and limited to relatively small populations of email users within organizations. In this paper, we report results of a large-scale study of more than 2 million users exchanging 16 billion emails over several months. We quantitatively characterize the replying behavior in conversations within pairs of users. In particular, we study the time it takes the user to reply to a received message and the length of the reply sent. We consider a variety of factors that affect the reply time and length, such as the stage of the conversation, user demographics, and use of portable devices. In addition, we study how increasing load affects emailing behavior. We find that as users receive more email messages in a day, they reply to a smaller fraction of them, using shorter replies. However, their responsiveness remains intact, and they may even reply to emails faster. Finally, we predict the time to reply, length of reply, and whether the reply ends a conversation. We demonstrate considerable improvement over the baseline in all three prediction tasks, showing the significant role that the factors that we uncover play, in determining replying behavior. We rank these factors based on their predictive power. Our findings have important implications for understanding human behavior and designing better email management applications for tasks like ranking unread emails.Comment: 11 page, 24th International World Wide Web Conferenc

Flux profile scanners for scattered high-energy electrons

The paper describes the design and performance of flux integrating Cherenkov scanners with air-core reflecting light guides used in a high-energy, high-flux electron scattering experiment at the Stanford Linear Accelerator Center. The scanners were highly radiation resistant and provided a good signal to background ratio leading to very good spatial resolution of the scattered electron flux profile scans.Comment: 22 pages, 17 figure

The clinical translation of plastic scintillation dosimetry

Contemporary radiotherapy focuses on achieving the best patient outcomes by delivering highly targeted treatments that often include small fields and high dose gradients. Plastic scintillators outperform traditional dosimeters in these fields as they are close to water-equivalent. However, the translation of scintillation dosimeters into the clinic has been limited by three roadblocks. The generation of Cerenkov radiation in an optic fibre irradiated by megavoltage radiation contaminates the scintillation signal. Two Cerenkov removal methods (spectral discrimination and air core) were found to be accurate in accounting for Cerenkov radiation and their clinical robustness was improved. The light readout system is often the limiting factor for the accuracy of scintillators. PMTs outperform camera-based systems, though their implementation for array dosimetry is complex. A novel system with a multianode PMT was constructed and enabled multiple light signals from an array to be simultaneously measured. Arrays of scintillation dosimeters are difficult to create due to the complex arrangement of detectors and their optical pathways. Two innovative approaches (square waveguides and 3D printing) were used to build prototype scintillation dosimeter arrays. These arrays showed that scintillation dosimeters can measure dose distributions with high spatial and temporal resolution. Addressing these roadblocks has enabled the clinical translation of scintillation dosimeters. In small field dosimetry, an air core dosimeter was used as a reference to calculate and predict correction factors for existing dosimeters. For brachytherapy, an array of scintillators provided real-time dose measurements that improved the safety of the treatment. For rotational treatments, a cylindrical array was used to verify the dose delivered during simulated stereotactic treatments. Traditional dosimeters cannot be used in these applications and this demonstrates the potential of scintillation dosimetry