Bewitched by the Word "Know�

You ask me if our friend is in town, I say yes; you ask, "Are you sure?,� I reply, "I know it – I just installed him in our guest room!�—What if you're mistaken?—One can't be making a mistake about something like that!---So you"re claiming infallibility?—Saying "I can't be making a mistake" was just a way of saying "I know ...�; I wasn"t alleging a ridiculous "justification� for my claim!---But only the infallible possession of truth really justifies a claim to knowledge.— The "I know ...� is just an instrument with a limited, practical purpose -- a purpose which the following expansion of the "builder's language" helps to bring out: The number [of building stones] is sometimes estimated, sometimes established by counting. Then the question arises "Do you believe there are as many stones as that?,� and the answer "I know there are – I"ve just counted them.� But then the "I know� could be dropped. If, however, there are several ways of finding something out for sure, like counting, weighing, measuring the stack, then the statement "I know� can take the place of mentioning how I know. [Wittgenstein 1969, sec. 564

Joint preload properties of structural threaded fasteners

Proper installation techniques are described and reliable torque-tension values are presented on joint preload /or clamp load/ properties of structural threaded fasteners

On the arithmetic of tight closure

We provide a negative answer to an old question in tight closure theory by showing that the containment x^3y^3 \in (x^4,y^4,z^4)^* in K[x,y,z]/(x^7+y^7-z^7) holds for infinitely many but not for almost all prime characteristics of the field K. This proves that tight closure exhibits a strong dependence on the arithmetic of the prime characteristic. The ideal (x,y,z) \subset K[x,y,z,u,v,w]/(x^7+y^7-z^7, ux^4+vy^4+wz^4+x^3y^3) has then the property that the cohomological dimension fluctuates arithmetically between 0 and 1

Multi-Gigabit Wireless data transfer at 60 GHz

In this paper we describe the status of the first prototype of the 60 GHz wireless Multi-gigabit data transfer topology currently under development at University of Heidelberg using IBM 130 nm SiGe HBT BiCMOS technology. The 60 GHz band is very suitable for high data rate and short distance applications as for example needed in the HEP experments. The wireless transceiver consist of a transmitter and a receiver. The transmitter includes an On-Off Keying (OOK) modulator, an Local Oscillator (LO), a Power Amplifier (PA) and a BandPass Filter (BPF). The receiver part is composed of a BandPass- Filter (BPF), a Low Noise Amplifier (LNA), a double balanced down-convert Gilbert mixer, a Local Oscillator (LO), then a BPF to remove the mixer introduced noise, an Intermediate Amplifier (IF), an On-Off Keying demodulator and a limiting amplifier. The first prototype would be able to handle a data-rate of about 3.5 Gbps over a link distance of 1 m. The first simulations of the LNA show that a Noise Figure (NF) of 5 dB, a power gain of 21 dB at 60 GHz with a 3 dB bandwidth of more than 20 GHz with a power consumption 11 mW are achieved. Simulations of the PA show an output referred compression point P1dB of 19.7 dB at 60 GHz.Comment: Proceedings of the WIT201

Separation of suspended particles by arrays of obstacles in microfluidic devices

The stochastic transport of suspended particles through a periodic pattern of obstacles in microfluidic devices is investigated by means of the Fokker-Planck equation. Asymmetric arrays of obstacles have been shown to induce the continuous separation of DNA molecules of different length. The analysis presented here of the asymptotic distribution of particles in a unit cell of these systems shows that separation is only possible in the presence of a driving force with a non-vanishing normal component at the surface of the solid obstacles. In addition, vector separation, in which different species move, in average, in different directions within the device, is driven by differences on the force acting on the various particles and not by differences in the diffusion coefficient. Monte-Carlo simulations performed for different particles and force fields agree with the numerical solutions of the Fokker-Planck equation in the periodic system

Population-based monitoring of cancer patient survival in situations with imperfect completeness of cancer registration

Selective underascertainment of cases may bias estimates of cancer patient survival. We show that the magnitude of potential bias strongly depends on the time periods affected by underascertainment and on the type of survival analysis (cohort analysis vs period analysis). We outline strategies on how to minimise or overcome potential biases

Engineered bidirectional communication mediates a consensus in a microbial biofilm consortium

Microbial consortia form when multiple species colocalize and communally generate a function that none is capable of alone. Consortia abound in nature, and their cooperative metabolic activities influence everything from biodiversity in the global food chain to human weight gain. Here, we present an engineered consortium in which the microbial members communicate with each other and exhibit a “consensus” gene expression response. Two colocalized populations of Escherichia coli converse bidirectionally by exchanging acyl-homoserine lactone signals. The consortium generates the gene-expression response if and only if both populations are present at sufficient cell densities. Because neither population can respond without the other's signal, this consensus function can be considered a logical AND gate in which the inputs are cell populations. The microbial consensus consortium operates in diverse growth modes, including in a biofilm, where it sustains its response for several days