Hot Nonequilibrium Quasiparticles in Transmon Qubits.

Nonequilibrium quasiparticle excitations degrade the performance of a variety of superconducting circuits. Understanding the energy distribution of these quasiparticles will yield insight into their generation mechanisms, the limitations they impose on superconducting devices, and how to efficiently mitigate quasiparticle-induced qubit decoherence. To probe this energy distribution, we systematically correlate qubit relaxation and excitation with charge-parity switches in an offset-charge-sensitive transmon qubit, and find that quasiparticle-induced excitation events are the dominant mechanism behind the residual excited-state population in our samples. By itself, the observed quasiparticle distribution would limit T_{1} to ≈200 µs, which indicates that quasiparticle loss in our devices is on equal footing with all other loss mechanisms. Furthermore, the measured rate of quasiparticle-induced excitation events is greater than that of relaxation events, which signifies that the quasiparticles are more energetic than would be predicted from a thermal distribution describing their apparent density.

Deterministic Remote Entanglement of Superconducting Circuits through Microwave Two-Photon Transitions.

Large-scale quantum information processing networks will most probably require the entanglement of distant systems that do not interact directly. This can be done by performing entangling gates between standing information carriers, used as memories or local computational resources, and flying ones, acting as quantum buses. We report the deterministic entanglement of two remote transmon qubits by Raman stimulated emission and absorption of a traveling photon wave packet. We achieve a Bell state fidelity of 73%, well explained by losses in the transmission line and decoherence of each qubit.

Repeat microvascular decompression for hemifacial spasm.

OBJECTIVE: To report our experience with repeat microvascular decompression (MVD) for hemifacial spasm (HFS) in patients who have failed their first operation. METHODS: The authors describe 41 redo MVDs for HFS in 36 patients performed over a 3 year period. Seven patients underwent early re-operation after an aborted seventh nerve decompression. Eight patients underwent early re-operation for clinical failure. Eighteen patients underwent late re-operation for spasm recurrence long after their original MVD. Eight MVDs were performed on patients who had already undergone at least two prior operations. RESULTS: Twenty four patients experienced complete spasm resolution (70.6%), eight patients had near total resolution (23.5%), and two patients failed re-operation (5.9%). Two patients were lost to follow up (5.6%). A favourable outcome was reported by 82.4% of patients at a mean follow up interval of 18 months. A total of 91.7% of patients 50 years of age or younger were cured at follow up versus 59.1% of patients older than 50 (p = 0.04). Patients undergoing early re-operation were significantly more likely to be cured or improved than patients undergoing late re-operation (p = 0.03). CONCLUSIONS: Repeat MVD for HFS is effective in experienced hands. Younger patients respond better to repeat MVD. Late repeat MVD for HFS is a reasonable treatment option, although results are less favourable than for early re-operation.

Shp2 regulates SRC family kinase activity and Ras/Erk activation by controlling Csk recruitment.

The protein-tyrosine phosphatase Shp2 plays an essential role in growth factor and integrin signaling, and Shp2 mutations cause developmental defects and/or malignancy. Previous work has placed Shp2 upstream of Ras. However, the mechanism of Shp2 action and its substrate(s) are poorly defined. Additional Shp2 functions downstream of, or parallel to, Ras/Erk activation also are proposed. Here, we show that Shp2 promotes Src family kinase (SFK) activation by regulating the phosphorylation of the Csk regulator PAG/Cbp, thereby controlling Csk access to SFKs. In Shp2-deficient cells, SFK inhibitory C-terminal tyrosines are hyperphosphorylated, and the tyrosyl phosphorylation of multiple SFK substrates, including Plcgamma1, is decreased. Decreased Plcgamma1 phosphorylation leads to defective Ras activation on endomembranes, and may help account for impaired Erk activation in Shp2-deficient cells. Decreased phosphorylation/activation of other SFK substrates may explain additional consequences of Shp2 deficiency, including altered cell spreading, stress fibers, focal adhesions, and motility.

Staged removal of acoustic tumors: techniques and lessons learned from a series of 83 patients.

The removal of large acoustic tumors is associated with increased mortality and cranial nerve injury. One method for treating these difficult lesions is staged resection. Between 1972 and 1992, more than 600 acoustic tumors were resected at our institution. Of these, 83 were removed in stages. This represents the largest series of staged acoustic tumor resections reported to date. A review of available films and patient records was performed for all acoustic tumors resected in stages between 1972 and early 1993 to analyze demographic information, tumor size, operative technique, outcome, and complications. The information was collected on standardized data sheets and entered into a computer database. Virtually all tumors were large, with the average size being 4 cm in greatest diameter. The average patient age was 41 years, and there was a slight preponderance of female patients. Ten patients had neurofibromatosis Type 2. The suboccipital approach was used in most patients. Anatomic preservation of the VIIth cranial nerve was achieved in > 72% of patients, with an average House-Brackmann score of Grade 3 at the longest follow-up (mean, 43 mo). Facial reanimation was performed in 19 of 23 patients with transected VIIth cranial nerves. Complications included cerebrospinal fluid fistulas in 11 patients, with 8 of 11 fistulas resolving after lumbar drainage. Six patients had meningitis (bacterial in three and aseptic in three). Two patients developed wound infections, and 10 patients developed exposure keratitis. There were two documented recurrences. There were no operative deaths. In most series, the incidence of cranial nerve deficits as well as morbidity and mortality is directly related to tumor size. Our operative strategy involved debulking the lateral aspect of large tumors during Stage I. Second stage removal is performed after the remaining tumor is shown to decompress out of the pons on computed tomographic or magnetic resonance images. During the second procedure, the residual tumor is less vascular and no longer densely adherent to the brain stem. Although staged removal is not without risk, there seems to be no apparent increase in morbidity when these results are compared with the results of series from the literature. Although there remain no absolute indications for staged resection of acoustic tumors, we think that it may represent the safest option for these difficult lesions.

False negative breast biopsy for palpable mass.

Open breast biopsy is considered to be the most reliable method for the diagnosis of breast cancer in patients with palpable masses. Rarely, after a breast biopsy has been reported to be benign, cancer will be identified at the site of the biopsy. Eight patients were reviewed in whom breast cancer was demonstrated at the site of a previously negative biopsy at intervals ranging between 4 months and 3 years after the original, negative biopsy. Several possible explanations exist to account for this occurrence. The surgeon must be aware that the presence of a mass at the site of prior breast biopsy may be an indication for repeat excision.

The nurse's role as clinical coordinator for the Center for Cranial Base Surgery.

The newly created position of clinical coordinator for the Center for Cranial Base Surgery at Presbyterian-University Hospital is detailed in this article. The position evolved in response to needs of this specialized center, because the complexities of cranial base tumors (CBTs) require optimal patient care be a collaborative effort. The clinical coordinator works with the neurosurgeon in all phases of treatment. From the preoperative visit, through admission and surgery, and then in postoperative care and follow-up, patient care is centered not only on the physical aspects inherent in surgery and recovery, but also on psychological support and attention which must be maintained throughout the patient's treatment course. In addition, the clinical coordinator has important input concerning research activities, particularly in clinical implementation of new therapies, as well as patient data management. Inservice education of other health professionals in their dealings with CBT patients further enhances quality of and continuity in patient care. Patient-care responsibilities as well as related research and training activities are discussed.

The gibberellin synthesis inhibitors, ancymidol and flurprimidol, promote in vitro rooting of white pine microshoots.

Ancymidol and flurprimidol were tested for their ability to induce in vitro rooting on axillary proliferated shoots of white pine (Pinus strobus L.). Shoots were treated for 30 days (pulse) with growth regulators, then subcultured to 0.5X medium for conifer morphogenesis without growth regulators. A pulse treatment containing 5 µM ancymidol and 0.54 µM naphthaleneacetic acid resulted in 43% rooted shoots, whereas a pulse treatment with 0.54 µM naphthaleneacetic acid alone resulted in 7% root formation. Flurprimidol also stimulated rooting of white pine shoots, but was less effective than ancymidol. No detrimental effects on shoot growth were observed with the gibberellin synthesis inhibitors at the 5 µM concentration used. Some rooted shoots were successfully acclimatized to the greenhouse.

Meningiomas involving the clivus: a six-year experience with 41 patients.

A series of 41 meningiomas involving the clivus operated on from July 1983 to January 1990 is reported. The presenting symptoms and signs of these patients were similar to those reported previously. All the patients were evaluated by pre- and postoperative thin-section, high-resolution computed tomography using soft tissue and bone algorithms. Most of the patients also underwent magnetic resonance imaging. The regions of the clivus involved by tumor were divided into upper, middle, or lower regions on the basis of anatomical landmarks. The diameter of the tumor was measured in three axes, and a tumor volume and a tumor equivalent diameter were computed to categorize tumors as small, medium, large, or giant types. There were 9 medium, 27 large, and 5 giant tumors in this series. Some simple and some complex operative approaches were employed to effect tumor removal. Large and giant tumors often required more than one operative approach to remove the tumor. Intraoperative technical difficulties included tumor consistency, vascularity, dissection from the brain stem, and vascular and cranial nerve encasement. Postoperative computed tomographic scans documented total excision in 32 patients (78%). Residual tumor remained in the clival or cavernous sinus areas. These patients were either being observed, or were treated with gamma knife radiosurgery. There was one operative death due to pneumonia (2%), and three patients (7%) suffered permanent major neurological changes, presumably due to vascular occlusions in the posterior circulation. In the follow-up period, which ranged from 3 to 76 months, 2 patients (6%) with tumors that had appeared to be totally excised experienced recurrence. These patients were treated by a second operation, alone or in combination with radiation therapy. Two patients who had subtotal excisions (25%) had evidence of regrowth. In 2 patients, tumor growth continued despite gamma knife radiosurgery or external beam radiotherapy.

Protein synthesis in perfused rat lungs: determinations based on incorporation of radioactive proline.

Functional compartmentation and metabolism of radioactive proline was evaluated to define conditions under which synthesis of lung proteins could be measured accurately based on proline incorporation. Rat lungs were perfused with Krebs-Henseleit bicarbonate buffer equilibrated with O2/N2/CO2 (20:75:5) and containing 4.5% (w/v) bovine serum albumin, 5.6 mM glucose and amino acids at plasma levels. Intracellular proline increased linearly as perfusate proline concentration was increased from 108 microM, the plasma level, to 540 or 1080 microM. At each concentration, the pool of proline which provided precursors to protein synthesis rapidly reached a steady-state specific radioactivity, but when extracellular proline was 108 microM, this pool was diluted significantly by proline from endogenous sources. At 540 or 1080 microM extracellular proline, the specific radioactivities of perfusate and intracellular proline approached equality and rates of protein synthesis calculated based on the specific radioactivity of extracellular proline compared favorably with those calculated from the specific radioactivity of phenylalanyl-tRNA. Similar results were obtained in lungs of two groups of rats in which intracellular proline concentration differed 3-fold. Thus, the contribution of endogenous proline to the pathway of protein synthesis was minimized when extracellular proline was present at high concentration. Under this condition, calculations of protein synthesis based on proline incorporation were most accurate.

Lung growth in response to unilateral pneumonectomy in rapidly growing rats.

The rapidity with which lung growth is initiated and completed after pneumonectomy was examined in young rats (4 wk of age; 82 g). After left pneumonectomy, the remaining lobes of the right lung grew to equal the weight of both lungs of control animals by day 7 and within 14 days increased from 366 to 968 mg. The tissue concentrations of RNA, DNA phosphate, collagen, and noncollagen proteins did not increase during the growth response. In contrast, total amounts of these constituents increased significantly in the remaining lung of pneumonectomized animals during the 1st postoperative wk and approached levels found in both lungs of sham-operated and unoperated controls by the end of the 2nd wk after pneumonectomy. Although cell size increased in control lungs during the experimental period, there was little evidence of additional cellular hypertrophy associated with compensatory lung growth. The character of the response to pneumonectomy in these rats was similar to that observed previously in older animals (320 g). Thus in spite of the higher basal rate of lung growth in the younger rats, the pattern and rapidity of compensation after pneumonectomy was similar in both age groups.

Effect of age on the accumulation of lung protein following unilateral pneumonectomy in rats.

The effects of unilateral pneumonectomy (PNX) on the net synthesis of right lung protein were investigated in vivo using three groups of rats with body weights (BW) ranging from 85 to 330 g. These data were compared to those from sham-operated and normal growing control animals. After PNX, both the 2-day lag prior to the compensatory increase in right lung mass (LW) and the subsequent rate of increase in LW and LW/BW ratio were independent of two-fold differences in the basal rate of lung growth. In all PNX groups, both right LW and LW/BW reached control values for both lungs, but in the older rats the time required for complete compensation was extended from 5 days to 12 days. The rate of net accumulation of right lung protein increased two-fold in the youngest PNX rats and 6 to 8-fold in the older animals, but when these changes were normalized to the protein content of the remaining tissue, the older rats appeared to respond to PNX less efficiently. Increased tissue levels of RNA and the resulting increased capacity of the lungs for protein synthesis could account for the accelerated rate of gain in right lung protein following PNX in both adult and young animals.