Compact digitally tunable laser

We present a new design for a digitally tunable laser using two waveguide grating routers with different free spectral range. For an N-channel device, both the number of required amplifiers and the number of required grating arms scale as the square root of N, resulting in a more compact device than previously demonstrated and better scaleability. Contrary to previously demonstrated devices with a reduced number of amplifiers, all wavelength channels are multiplexed together in one common channel, allowing for a higher output power. Tuning speeds below 10 ns are envisioned. Experimental results are presented.     

Monolithic demodulator for 40-gb/s DQPSK using a star coupler

A novel device that demodulates both quadratures of the optical differential quadrature phase-shift keying (DQPSK) format in a single interferometer by using a 4 /spl times/ 4 star coupler was demonstrated. Simultaneous measurements of both DQPSK quadratures at 42.7 Gb/s are also presented.     

Improvement in tool life of coated high speed steel drills using the activated reactive evaporation process

Type M-10 high speed steel drills of diameter 0.25 in were coated with TiC and TiN using the activated reactive evaporation process. The coated drills were tested by drilling holes into plates of AISI 4150 steel of thickness 1 in at a hardness level of 300 HB. The speed used was 900 rev min^-1 and the feed rate was 0.007 in rev^-1. For comparison, uncoated and the standard black-oxide-coated drills were also tested using the same conditions. The average number of holes to failure was seven for uncoated drills, 33 for black-oxide-coated drills and 141 for the TiC- and TiN- coated drills. These results show that the TiC- and TiN-coated drills have tool lives of 20 times that of uncoated drills and 4.2 times that of black-oxide-coated drills under these test conditions.Torque and thrust measurements were made during the drilling test of same steel plates at 770 rev min^-1 and a feed rate of 0.008 in rev^-1 at Lockheed Company of California, Burbank. The TiC- and TiN-coated drills showed 15%-18% less thrust, 10%-23% less torque and eight to ten times the tool life of uncoated drills under these conditions. They also showed 15%-18% less thrust and 2.5 to three times the tool life in relation to the black-oxide-coated drills.     

25.6-Tb/s WDM Transmission of Polarization-Multiplexed RZ-DQPSK Signals

We demonstrate record 25.6-Tb/s transmission over 240 km using 160 WDM channels on a 50-GHz grid in the C+L bands. Each channel contains two polarization-multiplexed 85.4-Gb/s RZ-DQPSK signals, yielding a spectral efficiency of 3.2b/s/Hz in each band.     

40-wavelength rapidly digitally tunable laser

We present a tunable laser based on an N₁×N₂ chirped waveguide grating router that has N₁N₂ wavelengths, accessible in a digitally rapid manner, and only N ₁+N₂+1 semiconductor optical amplifiers. By using chirp, the free-spectral range of the router can be significantly less than the channel span. The version demonstrated here has N₁=5, N₂=8, a channel spacing of 100 GHz, and the router free-spectral range is only 20 channels     

Playing Mastermind with Constant-Size Memory

We analyze the classic board game of Mastermind with n holes and a constant number of colors. The classic result of Chvátal (Combinatorica 3:325–329, 1983) states that the codebreaker can find the secret code with Θ(n/logn) questions. We show that this bound remains valid if the codebreaker may only store a constant number of guesses and answers. In addition to an intrinsic interest in this question, our result also disproves a conjecture of Droste, Jansen, and Wegener (Theory Comput. Syst. 39:525–544, 2006) on the memory-restricted black-box complexity of the OneMax function class.     

A nuclear physics method for the determination of hydrogen diffusion coefficients

Hydrogen diffusion in titanium and Ti alloys was studied with a nuclear physics method based on the reaction ${}^{15}\text{N}\text{+}{}^1\text{H}\text{→}{}^{12}\text{C}\text{+}{}^4\text{He}\text{+ γ (4.43}\text{MeV}\text{)}$. The method and its applications for measuring lateral and depth hydrogen concentration profiles are described. Experiments were made with α Ti at 176°C, with Ti-6Al-4V as well as with γ Ti and Ti-0.5Ni. Results are compared with those obtained with the electrochemical pulse method. The advantages of the nuclear physics method are discussed.     

Application of USAF G-suit technology for clinical orthostatic hypotension: a case study

INTRODUCTION: The purpose of this study was to determine the effectiveness of a USAF anti-gravity suit (G-suit) on the stability of a patient with chronic orthostatic hypotension. METHODS: A 37-yr-old female with a history of insulin-dependent diabetes mellitus (IDDM) and symptomatic orthostasis was evaluated and the results were compared with those of non-diabetic controls, matched for age, height, and weight. Cardiac vagal tone was assessed by determination of standard deviation of 100 R-R intervals (R-R SD). We assessed the carotid-cardiac baroreflex response by plotting R-R intervals (ms) at each of eight neck pressure steps with their respective carotid distending pressures (mm Hg). Heart rate and blood pressure were recorded in response to the Valsalva maneuver (VM) performed at an expiratory pressure of 30 mmHg to assess integrated baroreflex responses. Blood pressures and heart rate were measured during three 5-min stand tests to assess orthostatic responses: a) without G-suit; b) with noninflated G-suit; and c) with inflated G-suit (50 mm Hg). RESULTS: The IDDM patient had minimal baseline cardiac vagal tone (R-R SD = 8.5 ms) compared with the average response of a control group of 24 subjects with orthostatic stability (R-R SD = 67.2 +/- 7.1 ms). Carotid-cardiac baroreflex response was virtually non-existent in the IDDM patient (Gain = 0.06 ms.mm Hg-1) compared to the control subjects (4.4 +/- 0.8 ms.mm Hg-1). VM responses corroborated the lack of cardiac baroreflex response in the IDDM patient, while blood pressure changes during the VM were similar to those of the controls. Upon standing, the IDDM patient demonstrated severe orthostatic hypotension (90 mm Hg SBP) and tachycardia without the G-suit. The G-suit, with and without pressure, reduced hypotension and tachycardia during standing. CONCLUSION: These results demonstrate successful application of Air Force technology as a useful alternative to pharmacologic intervention in the treatment of a patient with autonomic dysfunction leading to supine hypertension and orthostatic hypotension.     

Expression of human leukocyte antigens class I and class II on cultured biliary epithelial cells after cytomegalovirus infection

The influence of cytomegalovirus (CMV) infection on the HLA expression on cultured biliary epithelial cells (BEC) was investigated. CMV-infection augmented expression of HLA class I but not of HLA class II. CMV reduced the IFN-gamma-mediated induction of the de novo expression of HLA class II while the stimulated expression of HLA class I was not impaired. Autologous but not allogeneic PBL responded to CMV-infected BEC. This response resulted in upregulation of HLA class I on BEC which was significantly higher compared with the expression on infected BEC alone or on uninfected BEC cocultured with autologous PBL. The results suggest that CMV modulates the immunogenic potential of BEC, which is important for the HLA and CMV-mediated pathomechanisms in vivo.