GRAPE-5: A Special-Purpose Computer for N-body Simulation

We have developed a special-purpose computer for gravitational many-body simulations, GRAPE-5. GRAPE-5 is the successor of GRAPE-3. Both consist of eight custom pipeline chips (G5 chip and GRAPE chip). The difference between GRAPE-5 and GRAPE-3 are: (1) The G5 chip contains two pipelines operating at 80 MHz, while the GRAPE chip had one at 20 MHz. Thus, the calculation speed of the G5 chip and that of GRAPE-5 board are 8 times faster than that of GRAPE chip and GRAPE-3 board. (2) The GRAPE-5 board adopted PCI bus as the interface to the host computer instead of VME of GRAPE-3, resulting in the communication speed one order of magnitude faster. (3) In addition to the pure 1/r potential, the G5 chip can calculate forces with arbitrary cutoff functions, so that it can be applied to Ewald or P^3M methods. (4) The pairwise force calculated on GRAPE-5 is about 10 times more accurate than that on GRAPE-3. On one GRAPE-5 board, one timestep of 128k-body simulation with direct summation algorithm takes 14 seconds. With Barnes-Hut tree algorithm (theta = 0.75), one timestep of 10^6-body simulation can be done in 16 seconds.Comment: 19 pages, 24 Postscript figures, 3 tables, Latex, submitted to Publications of the Astronomical Society of Japa

GRAPE-6: The massively-parallel special-purpose computer for astrophysical particle simulation

In this paper, we describe the architecture and performance of the GRAPE-6 system, a massively-parallel special-purpose computer for astrophysical $N$-body simulations. GRAPE-6 is the successor of GRAPE-4, which was completed in 1995 and achieved the theoretical peak speed of 1.08 Tflops. As was the case with GRAPE-4, the primary application of GRAPE-6 is simulation of collisional systems, though it can be used for collisionless systems. The main differences between GRAPE-4 and GRAPE-6 are (a) The processor chip of GRAPE-6 integrates 6 force-calculation pipelines, compared to one pipeline of GRAPE-4 (which needed 3 clock cycles to calculate one interaction), (b) the clock speed is increased from 32 to 90 MHz, and (c) the total number of processor chips is increased from 1728 to 2048. These improvements resulted in the peak speed of 64 Tflops. We also discuss the design of the successor of GRAPE-6.Comment: Accepted for publication in PASJ, scheduled to appear in Vol. 55, No.

The application of pesticides to grape bunches

The application of pesticides to grape bunches is complicated by the different shapes and forms of the grape bunch during growth. Initially the grape bunch has a very porous structure, while in later stages the grapes are closely packed. We consider estimates of the flow velocity through the grape bunch, droplet density within the spray, probability of droplet impaction on a bunch or individual grape and the maximum size of drop that can adhere to a grape surface

Direct Simulation of Dense Stellar Systems with GRAPE-6

In this paper we describe the current status of the GRAPE-6 project to develop a special-purpose computer with a peak speed exceeding 100 Tflops for the simulation of astrophysical N-body problems. One of the main targets of the GRAPE-6 project is the simulation of dense stellar systems. In this paper, therefore, we overview the basic algorithms we use for the simulation of dense stellar systems and their characteristics. We then describe how we designed GRAPE hardwares to meet the requirements of these algorithms. GRAPE-6 will be completed by the year 2001. As an example of what science can be done on GRAPE-6, we describe our work on the galactic center with massive black holes performed on GRAPE-4, the predecessor of GRAPE-6.Comment: 12 pages, to appear in Dynamics of Star Clusters and the Milky Way, eds. R. Spurzem et al. (ASP Conference Series

Pseudoparticle Multipole Method: A Simple Method to Implement High-Accuracy Treecode

In this letter we describe the pseudoparticle multipole method (P2M2), a new method to express multipole expansion by a distribution of pseudoparticles. We can use this distribution of particles to calculate high order terms in both the Barnes-Hut treecode and FMM. The primary advantage of P2M2 is that it works on GRAPE. GRAPE is a special-purpose hardware for the calculation of gravitational force between particles. Although the treecode has been implemented on GRAPE, we could handle terms only up to dipole, since GRAPE can calculate forces from point-mass particles only. Thus the calculation cost grows quickly when high accuracy is required. With P2M2, the multipole expansion is expressed by particles, and thus GRAPE can calculate high order terms. Using P2M2, we implemented an arbitrary-order treecode on GRAPE-4. Timing result shows GRAPE-4 accelerates the calculation by a factor between 10 (for low accuracy) to 150 (for high accuracy). Even on general-purpose programmable computers, our method offers the advantage that the mathematical formulae and therefore the actual program is much simpler than that of the direct implementation of multipole expansion.Comment: 6 pages, 4 figures, latex, submitted to ApJ Letter

Lewiston Journal Article, Meat Inspection

Letter on the debate to regulate meat production under current state or federal inspection regulations.https://digitalcommons.usm.maine.edu/michaud-mailhot/1002/thumbnail.jp

Perineal hernia : retrospective study of contralateral hernia after unilateral surgery

Bakgrund: Det har föreslagits att perinealbråck hos hundar möjligtvis ska betraktas som en bilateral företeelse istället för unilateral. Det finns dock endast begränsad mängd data med avseende på risk för kontralateral operation efter åtgärd av unilateralt bråck. Syfte: Hypotesen var att behov av operation på kontralateral sida var sällsynt. Målet med studien var att undersöka förekomsten av kontralateral operation efter ett unilateralt ingrepp hos hund diagnostiserad med och behandlad för unilateralt perinealbråck. Metod och Material: En retrospektiv kohortstudie genomfördes där en sökning gjordes på debiteringskoder för operation av perinealbråck omfattande en period över tio år. Journaler som identifierades i sökningen analyserades. Sökningen avgränsades till operationer genomförda under åren 2009–2018 vid universitetsdjursjukhuset i Uppsala, Sverige. Gruppering av hundarna genomfördes från grupp ett till fem, där grupp ett bestod av de hundar med initialt enkelsidigt bråck, grupp två bestod av de initialt dubbelsidiga hundarna, grupp tre bestod av de hundar med tydligt bråck på ena sidan och med måttligt bråck på motsatta sidan, grupp fyra bestod av de hundar med tydligt bråck på ena sidan och ett lindrigt bråck på den motsatta sidan och grupp fem bestod av de hundar som hade tydligt bråck på ena sidan men motsatta sidan hade inget utvecklat bråck utan endast kommentar om bland annat försvagad muskulatur. I en fördjupad analys kontaktades vissa av djurägarna till grupp ett, alltså de hundarna med endast initialt enkelsidigt perinealbråck, som inte hade någon notering om försvagning i muskelväggen eller ett ytterligare bråck på den kontralaterala sidan. De djurägare där informationen saknades, om deras hund hade behövt uppsöka veterinärvård på grund av att ett kontralateralt bråck uppstått eller ej, kontaktades. Metoderna som användes vid kontaktande av djurägarna var telefonsamtal och SMS. Frågor som ställdes var bland annat om hunden hade utvecklat problem med den kontralaterala sidan och om det i så fall hade behövts åtgärdas kirurgiskt samt ålder på hunden vid uppkomst av eventuella problem. Om hunden var avliden ställdes frågan om hunden avlidit till följd av perinealbråcket eller av annan orsak. Resultat: Studien identifierade totalt 80 hanhundar. Grupp ett, initialt enkelsidigt bråck, bestod av 30 hundar. Grupp två, initialt dubbelsidiga bråck, konstaterades hos 24 hundar. Grupp tre bestod av två hundar som registrerades med tydligt bråck på ena sidan och måttligt bråck på den motsatta sidan. Grupp fyra bestod av fem hundar som registrerades med tydligt bråck på ena sidan och lindrigt bråck på motsatta sidan. Grupp fem bestod av 19 hundar som registrerades med tydligt bråck på ena sidan och en journalanteckning att motsatta sidans muskulatur uppfattades som slapp eller mer eftergivlig, utifrån en subjektiv bedömning vid rektalpalpation. Totala antalet registrerade operationer blev 98 varav 33 exklusive kastration och 65 inklusive kastration. 15 hundar opererades bilateralt i två steg varav 14 av dem var registrerade som grupp 2, initial som dubbelsidiga bråck, och en hund registrerades i grupp 5, slapp muskulatur på den motsatta sidan. Medelåldern vid operation av perinealbråck var 8,3 år (3,9–14,8 år) och medelvikten var 18,2 kg (3,5–49 kg). Utvecklande av kontralaterala perinealbråck hos initialt unilaterala bråck, grupp ett, sågs hos fem av 30 hundar. Två av de fem hundarna åtgärdades kirurgiskt och en hund behandlades konservativt och två avlivades på grund av det kontralaterala bråcket. Av de i grupp ett, initialt enkelsidigt bråck, som ej utvecklade bråck på kontralaterala sidan blev två avlivade under operation, en hund avlivades efter två månader på grund av återfall av bråck på samma sida och en hund avlivades fem månader efter operationen på grund av annan orsak som inte hade med perinealbråcket att göra. Utöver dessa fyra hundar var tiden från operation till uppföljning angående kontralateralt bråck hos grupp ett, initialt enkelsidiga, Sammanfattning mellan 11 månader–11,8 år och ett medelvärde på fyra år efter operation. De fyra hundarna som avlivades i samband med operation eller kort tid efter genomförd kirurgi valdes att i denna studie exkluderas. Totalt kontaktades 19 djurägare via telefon och/eller med sms med standardiserade frågor varav 15 djurägare svarade via telefonsamtal, två djurägare endast via sms och två djurägare svarade aldrig. Genom denna intervju identifierades två av de fem hundarna som utvecklade kontralateralt bråck. De två hundar vars djurägare inte lyckades kontaktas exkluderades. Detta medförde att fem hundar av de 24 hundar med initialt enkelsidigt perinealbråck, 20,8 %, utvecklade ett kontralateralt bråck på den motsatta sidan. Hos de hundar som hade bråck på ena sidan samt notering om försvagad muskulatur på motsatta sidan, grupp fem, behövde en hund uppsöka veterinärvård samt åtgärdas kirurgiskt på grund av att ha utvecklat perinealbråck på den motsatta sidan. Av de hundar som var registrerade som grupp 2–5, avlivades två i samband med operation på grund av dålig prognos och en strax efter operation på grund av komplikationer som krävde en ny operation. Dessa tre hundar valdes även de att exkluderas då de inte bedömdes ha chansen att kunna utveckla ett kontralateralt perinealbråck. Ytterligare två hundar avlivades 2,3 år och 4 år efter operationen på grund av problem med den genomförda bråckoperationen. Ytterligare fem hundar registrerades som avlidna på grund av annan orsak. En hund med initialt dubbelsidigt perinealbråck, grupp två, rekommenderades avlivning på grund av tumörsjukdom. 23 hundar, i grupperna 2–5, hade ingen journalanteckning varken om avlivning eller om en ny operation hade genomförts på den icke opererade sidan. Det medförde att i grupp 2–5 behövde en hund av 32 (50 hundar minus de 15 hundar som opererades i två steg, minus de tre avlidna hundarna som inte hade en chans att utveckla problem på motsatta sidan, då de avlivades under operation eller precis efter operationen) behövde uppsöka veterinärvård och åtgärdas kirurgiskt på grund av problem med den motsatta sidan. Det medför att av totalt 56 (24+32) enkelsidigt åtgärdade hundar sågs kontralateralt bråck sammanlagt hos sex hundar, 10,7 %. Diskussion: Resultaten av denna studie gav svagt eller inget stöd för rekommendationen att perinealbråck bör opereras bilateralt, om hunden har enkelsidigt bråck vid den kliniska undersökningen. Indikation gavs även att hundar som opererats enkelsidigt även fast de har lindrigt, måttligt eller påbörjan till perinealbråck kontralateralt, inte behöver opereras bilateralt rutinmässigt. I denna studie hittades fall där operation senare utfördes på den kontralaterala sidan, både när diagnosen initialt var enkelsidigt bråck eller en journalanteckning angående tecken på försvagad muskelvägg kontralateralt. Studiens huvudbegränsningar: Studien var retrospektiv och begränsad till endast patientjournaler från universitetsdjursjukhuset i Uppsala. Olika veterinärer gjorde undersökningarna och bedömningen om muskelväggen var intakt, eller försvagad, om förändringen klassades som lindrigt bråck eller fullt utvecklat bråck var subjektiv. Retrospektiv klassificering och gradering av bråckets omfattning baserat på journalanteckningar är mycket begränsad. Viss information var inhämtad genom telefonkontakt med djurägare som kan minnas fel. Vetenskaplig eller klinisk relevans: Denna studie visade inget stöd för att kontralateral operation rutinmässigt ska rekommenderas efter diagnostisering av ett enkelsidigt perinealbråck.Reasons for performing the study: It has been discussed whether perineal hernia in dogs should possibly be considered a bilateral phenomenon instead of unilateral. However, evidence is limited regarding the risk of the need of contralateral surgery after unilateral hernia. Purpose: The hypothesis was that the need for surgery on the contralateral side was rare. The aim of the study was to investigate the prevalence of contralateral surgery after unilateral procedure in dogs diagnosed with and treated for unilateral perineal hernia. Methods: A retrospective cohort study was conducted where a search was made in the medical record database for dogs subjected to surgery due to perineal hernia covering a period over ten years. The identified patient records were analysed. The dogs were operated during the years 2009-2018 at the University Animal Hospital in Uppsala, Sweden. The patients were divided in groups from one to five, where group one consisted of the dogs with initially single-sided hernia, group two consisted of the initially double-sided dogs, group three consisted of those dogs with clear hernia on one side and with moderate hernia on the opposite side, group four consisted of the dogs with clear hernia on one side and a mild hernia on the opposite side and group five consisted of the dogs that had clear hernia on one side but the opposite side had no developed hernia but patient record comments about weakened muscles. In an in-depth analysis, some of the animal owners of dogs in group one was contacted, i.e. the dogs with only initial unilateral perineal hernia, who had no note of weakness in the muscle wall or a further hernia on the contralateral side. The pet owners where the information was missing, whether their dog had had to seek veterinary care due to a contralateral hernia or not, were contacted. The methods used when contacting the animal owners were telephone calls and text message. Questions that were asked included whether the dog had developed problems with the contralateral side and whether in that case surgical action had been needed as well as the age of the dog when any problems arose. If the dog had died, the question was asked whether the dog had died as a result of perineal hernia or for some other reason. Results: The study identified a total of 80 male dogs. Group one, initially unilateral hernia consisted of 30 dogs. Group two, initially bilateral hernia was found in 24 dogs. Group three consisted of two dogs. Group four consisted of five dogs registered with clear hernia on one side and mild hernia on the opposite side. Group five consisted of 19 dogs that were registered with a clear hernia on one side and a note that the opposite muscle wall was perceives as flaccid, based on subjective assessment at rectal palpation. The total number of registered operations was 98, of which were 33 excluding castration and 65 including castration. 15 dogs were bilaterally operated on in two stages, of which 14 were initially registered as group two, initial as bilateral hernias, and one dog was registered in group five, loose muscle on the opposite side. The mean age at perineal hernia surgery was 8.3 years (3.9–14.8 years) and the average weight was 18.2 kg (3.5–49 kg). Development of contralateral perineal hernia in initially unilateral hernia, group one, was seen in five of 30 dogs. Two of the five dogs were treated surgically, and one dog was treated conservatively and two were euthanized due to the contralateral hernia. Of those in group one, initially unilateral hernia, who did not develop hernia on the contralateral side, two were euthanized during surgery, one dog was euthanized after two months due to recurrence of hernia on the same side and one dog was euthanized five months after surgery for another cause not related to the perineal hernia. In addition to these four dogs, the time from surgery to follow-up regarding contralateral hernia in group one, initially unilateral, was between 11 months – 11.8 years and an average of four years after surgery. The four dogs that were euthanized in connection with surgery or shortly after surgery were excluded in this Abstract study. A total of 19 pet owners were contacted by telephone and/or by text message with standardized questions, of which 15 pet owners answered via telephone calls, two pet owners only via text message and two pet owners never answered. Through this interview, two of five dogs that developed contralateral hernia were identified. The two dogs whose pet owners failed to be contacted were chosen to be excluded as well. This resulted in five dogs out of the 24 dogs with initially unilateral perineal hernia, 20.8 %, developed a contralateral hernia on the opposite side. In those dogs that had hernias on one side and a comment regarding weakened muscles on the opposite side, group five, only one dog needed to seek veterinary care and was treated surgically due to having developed perineal hernias on the opposite side. Of the dogs that were registered as groups 2-5, two were euthanized in connection with surgery due to a poor prognosis and one shortly after surgery due to complications that required a new operation. These three dogs were also chosen to be excluded as they were not judged to have the chance of developing a contralateral perineal hernia. Another two dogs were killed 2.3 years and four years after the operation due to problems with the hernia operation. Another five dogs were registered as dead due to another cause. A dog with initial bilateral perineal hernia, group two, was recommended for euthanasia due to tumour disease. 23 dogs, in group 2-5, had no medical record either about if the dogs had been euthanized or if a new operation had been performed on the non-operated side. This meant that in group 2-5, one dog of 32 (50 dogs minus the 15 dogs that were operated in two steps, minus the three deceased dogs that did not have a chance to develop problems on the opposite side, when they were euthanized during surgery or shortly after surgery) needed to seek veterinary care and be treated surgically due to problems with the opposite side. In summary, out of a total of 56 (24+32) unilaterally treated dogs, a total of contralateral hernia was seen in six dogs, 10.7 %. Discussion: Based on the result of this study there is little or no support to give a recommendation that dogs with a unilateral perineal hernia should be subjected to a bilateral surgery. Based on the results of this study, the recommendation is not to surgically treat a mild perineal hernia on the contralateral side beyond the side where the main hernia is located. This study indicates that these hernias usually do not need any form of surgical treatment. Main study Limitations: The study was retrospective and limited to the patient records from the University Animal Hospital in Uppsala, Sweden. Some information was obtained through telephone contact with pet owners who could remember incorrectly. Due to the retrospective nature of the study, the level of evidence regarding grading or scoring of hernia was considered low. Scientific or Clinical relevance: This study showed no support for contralateral surgery on a routine basis after diagnosis of unilateral perineal hernia

Lewiston Journal Article, Meat Petition

Newspaper article on meat processing as it pertains to Mailhot\u27s Sausage. (photocopy)https://digitalcommons.usm.maine.edu/michaud-mailhot/1001/thumbnail.jp

The Dream of Coming Home

In the Margaret Chase Smith Essay, Nancy Grape, retired editorial writer for the Portland Press Herald and Maine Sunday Telegram, reflects on the meaning of retirement, and how it is changing in Maine and elsewhere

High Performance Direct Gravitational N-body Simulations on Graphics Processing Units

We present the results of gravitational direct $N$-body simulations using the commercial graphics processing units (GPU) NVIDIA Quadro FX1400 and GeForce 8800GTX, and compare the results with GRAPE-6Af special purpose hardware. The force evaluation of the $N$-body problem was implemented in Cg using the GPU directly to speed-up the calculations. The integration of the equations of motions were, running on the host computer, implemented in C using the 4th order predictor-corrector Hermite integrator with block time steps. We find that for a large number of particles (N \apgt 10^4) modern graphics processing units offer an attractive low cost alternative to GRAPE special purpose hardware. A modern GPU continues to give a relatively flat scaling with the number of particles, comparable to that of the GRAPE. Using the same time step criterion the total energy of the $N$-body system was conserved better than to one in $10^6$ on the GPU, which is only about an order of magnitude worse than obtained with GRAPE. For N\apgt 10^6 the GeForce 8800GTX was about 20 times faster than the host computer. Though still about an order of magnitude slower than GRAPE, modern GPU's outperform GRAPE in their low cost, long mean time between failure and the much larger onboard memory; the GRAPE-6Af holds at most 256k particles whereas the GeForce 8800GTF can hold 9 million particles in memory.Comment: Submitted to New Astronom