Solidification Cracking Restraining Mechanism of Al-Cu-Mg-Zn Alloy Welds Using Cold Metal Transfer Technique

Aluminum alloy 7075 (with 7055 and 7150 filler wires) was welded using a digital welding machine that can switch arc mode between MIG, CMT and CMT+P modes. The transverse-motion weldability test of joints welded under different arc modes showed that the solidification cracking susceptibility was lower in CMT-technique-based welds than in MIG welds. The temperature cycle of the welding pool under different arc modes was recorded using mini-thermocouples, which showed that the cooling rate was lower in CMT welded samples than in MIG welded samples. The low cooling rate promoted the growth of α-Al dendrites through the back diffusion effect. Electron probe micro-analysis showed that micro-segregation of the α-Al dendrites was lower in the CMT welded samples than in the MIG welded samples. The T-(f_Al)^1/2 curve of each weld was calculated, which showed that CMT-based welding enhanced the bridging of adjacent α-Al dendrites, reducing the tendency for solidification cracking.

Characterisation and feasibility study for superradiant lasing in 40Ca atoms

Superradiant active clocks operating on narrow linewidth clock transitions are predicted to achieve precision orders of magnitude higher than any currently existing optical atomic clocks. We introduce a theory of superradiant lasing and implement it for the example of ⁴⁰Ca atoms. The presented model, however, is valid for any two- or three-level system in an optical lattice. We perform a feasibility analysis and suggest a set of parameters for the experimental fulfillment of superradiant lasing in Ca. Moreover, we present an overview of different magic wavelengths for the 4s^{2 1}S₀ ↔ 4s4p³P₁ (m_J = 0) transition in Ca for different polarizations and a robustness analysis of these magic conditions. We also report the magic-zero wavelengths for the 4s4p³P₁, m_J = 0 state.

New bounds on dark matter coupling from a global network of optical atomic clocks

We report on the first Earth-scale quantum sensor network based on optical atomic clocks aimed at dark matter (DM) detection. Exploiting differences in the susceptibilities to the fine-structure constant of essential parts of an optical atomic clock, i.e., the cold atoms and the optical reference cavity, we can perform sensitive searches for DM signatures without the need for real-time comparisons of the clocks. We report a two orders of magnitude improvement in constraints on transient variations of the fine-structure constant, which considerably improves the detection limit for the standard model (SM)-DM coupling. We use Yb and Sr optical atomic clocks at four laboratories on three continents to search for both topological defect and massive scalar field candidates. No signal consistent with a DM coupling is identified, leading to considerably improved constraints on the DM-SM couplings.

The effect of intravenous pamidronate on bone mineral density, bone histomorphometry, and parameters of bone turnover in adults with type IA osteogenesis imperfecta

The type IA osteogenesis imperfecta (OI) phenotype is characterized by multiple fractures, blue sclerae, and minimal skeletal deformity without dentinogenesis imperfecta. The object of this study was to determine the effect of treatment with intravenous pamidronate (30 mg) every 3 months on bone density and bone histomorphometry in adults with type IA OI. After an initial iliac crest bone biopsy eight subjects, 5 women and 3 men, entered a treatment program lasting 21-30 months. Five subjects, all women, completed the study which included a posttreatment iliac crest bone biopsy. Pamidronate treatment led to significant increases in bone mineral density (BMD), measured by DXA, in the lumbar spine at 12 months (P = 0.05) and in the femur neck (P = 0.02) at 24 months. Significant increases in BMD were also seen in femoral trochanter at 12 months (P = 0.05) and at 24 months (P = 0.02), and in Ward's triangle at 12 months (P = 0.02) and 24 months (P = 0.05). Mean osteocalcin levels decreased 32%, C-terminal procollagen peptide and bone alkaline phosphatase declined 12% and 47% at 15 and 21 months, respectively. Deoxypyridinoline crosslink excretion decreased 31%. Posttreatment bone biopsy revealed a significant 6.3% increase in mean bone trabecular volume (P = 0.01). Mean cortical thickness increased from 848 mm to 1384 mm (P = 0.01) and cortical porosity decreased 13.2% (P = 0.01). Bone formation rate increased significantly in all 5 patients from 6.6 to 15.3 mm2/yr (P = 0.01). Mineral apposition rate was unchanged. These results indicate that intravenous pamidronate, 30 mg every 3 months, may have significant effects on bone density and histomorphometry in adults with type IA OI. Responses at higher doses remain to be evaluated.

Direct mechanomyographic measurement of the myorelaxant action of baclofen and diazepam in normal and reserpinized rats

A pathologically increased muscle tone is frequently observed. Objective methods for measuring directly the muscle-relaxant action of drugs in laboratory animals are scarce. This study shows that a computerized mechanomyographic method allows the assessment of myorelaxant drugs. The method consists of the successive bending and straightening of the rat's foot in the ankle joint and the separate measurement of resistance of extensors and flexors of the hind foot to passive movements. The two well-known antispastic drugs diazepam and baclofen reduced the normal muscle tone in both groups of muscles in non-treated animals as well as the muscle tone increased by reserpine (10 mg/kg i.p.). The results obtained show that the mechanomyographic method directly and reliably reveals the myorelaxant action of drugs.

[Azoles. 12. Pyrazole carbolic acid thioamides]

Morpholids, N-methylpiperazids, piperidids and pyrrolidids of 5-methyl, 3,5-dimethyl-1-phenyl-4-pyrazolthioacetic acid and 3,5-dimethyl-1-phenyl-4-pyrazolcarbonic acid 4-12 are obtained by the Willgerodt-Kindler procedure. The oxothioamids 13-19 result as the intermediate products of the synthesis of thioamids 4-10. The compounds 4, 5, 8, 9, 11, 14 and 17 do not respond to Mycobacterium tuberculosis H37Rv. The thioamids 4, 8 and 11 are of slight toxicity (LD50 greater than 2.8 g/kg, albino-Swiss mice) and inhibit the Carrageenin oedema of the Wistar rat claw minor than phyenylbutazon and indometacin.